Magnesium salicylate

What it is

Magnesium salicylate is the magnesium salt of salicylic acid, sold in the United States as an over-the-counter oral pain reliever classed on its label as a non-steroidal anti-inflammatory drug. The Doan's Maximum Strength label states each caplet holds magnesium salicylate tetrahydrate 580 mg, equivalent to 467.2 mg of anhydrous magnesium salicylate, and that each caplet contains magnesium 45 mg. It is a non-acetylated salicylate: unlike aspirin it carries no acetyl group, and the acetyl group is what makes aspirin an irreversible platelet inhibitor. Products are marketed for backache rather than for any cardiovascular purpose.

What the research says

The evidence base here is remarkably thin for a drug sold on open shelves. We found no placebo-controlled outcome trial of magnesium salicylate for back pain in the literature we searched, so the single-ingredient back-pain claim rests on the FDA over-the-counter monograph position and the manufacturer's label rather than on published trials. What is well documented is the pharmacology it shares with other salicylates: it is a salicylate, so it carries the salicylate harms (stomach bleeding, Reye's syndrome in children and teenagers, tinnitus and hearing loss, salicylate poisoning), and, because it is non-acetylated, the platelet experiments show it does not block platelet aggregation the way aspirin does. That last point cuts both ways: it is a reason non-acetylated salicylates have been proposed for people with bleeding tendencies, and it is the reason aspirin's heart and stroke prevention trials cannot be read across to it.

Evidence grade: Limited evidence.

How it works

Drug class: Non-acetylated salicylate; non-steroidal anti-inflammatory drug (NSAID)

Magnesium salicylate dissociates to the salicylate anion, which is a weak inhibitor of the cyclo-oxygenase enzymes that make prostaglandins, so it damps pain and inflammation signalling. Unlike aspirin it has no acetyl group to transfer, so it does not permanently disable the cyclo-oxygenase enzyme inside platelets; experiments on a closely related non-acetylated salicylate found no inhibition of platelet aggregation at a salicylate dose matched to aspirin. (Source 1)

What it is used for

• This is the only use the US label claims, and it is a regulatory position rather than a trial result. We found no randomised placebo-controlled trial of magnesium salicylate for back pain; a 2026 systematic review and meta-analysis of oral NSAIDs in low back pain examined celecoxib, diclofenac, etoricoxib, ibuprofen, ketoprofen and naproxen, and magnesium salicylate was not among the drugs it could assess. Evidence: unknown. (Source 2)
• Small crossover studies in healthy volunteers and in people with haemophilia A found that non-acetylated salicylates did not prolong bleeding time or inhibit platelet aggregation, and their authors suggested these drugs as an aspirin alternative where bleeding is a concern. These are surrogate platelet-function studies in a few dozen people, not clinical bleeding-outcome trials, and they used choline magnesium trisalicylate and salsalate rather than magnesium salicylate itself. Evidence: limited. (Source 1)
• Aspirin's cardiovascular benefit is attributed specifically to irreversible acetylation of platelet cyclo-oxygenase-1, which a non-acetylated salicylate does not do. The platelet studies show no aggregation inhibition from non-acetylated salicylate at matched salicylate exposure, so aspirin's outcome trials are not evidence for magnesium salicylate. Evidence: not-supported. (Source 3)

Interactions

• Alcohol (label): The label names three or more alcoholic drinks a day while using the product as a factor that raises the chance of severe stomach bleeding. (Source 2)
• Aspirin and other NSAIDs (ibuprofen, naproxen and others) (label): Taking another NSAID at the same time raises the chance of severe stomach bleeding; the label treats prescription and non-prescription NSAIDs alike. (Source 2)
• Anticoagulants (blood thinners) and oral steroids (label): Concurrent anticoagulant or steroid raises the chance of severe stomach bleeding. (Source 2)
• Diuretics (label): The label tells people taking a diuretic to ask a doctor before use; salicylates and diuretics both act on the kidney. (Source 4)
• Prescription drugs for gout, diabetes or arthritis (label): The label singles out these three drug groups for a pharmacist or doctor check before use. (Source 4)
• Magnesium supplements and magnesium-containing laxatives or antacids (case reports): Each caplet carries magnesium 45 mg, so eight caplets a day add 360 mg of magnesium on top of anything else taken. In people with reduced kidney function, magnesium-containing oral products have caused severe and occasionally fatal hypermagnesemia; the published cases used magnesium oxide rather than magnesium salicylate, so this is an inference from the shared magnesium load rather than a documented interaction for this salt. (Source 5)
• Aspirin, in people whose asthma aspirin triggers (clinical trial): A non-acetylated salicylate given before aspirin blunted the aspirin reaction in aspirin-intolerant patients, which tells you the two interact at the cyclo-oxygenase site in the airway. This was studied with choline magnesium trisalicylate, not magnesium salicylate. Limit: The salicylate given in this study was choline magnesium trisalicylate, not magnesium salicylate, and only nine aspirin-intolerant patients took part; the nasal result rests on three of five. The authors call the effect moderate protection and say the mechanism is unknown. Nothing here suggests taking one salicylate to make aspirin safer. (Source 6)

Stopping it

• We found no withdrawal syndrome, rebound or tapering literature for magnesium salicylate. The label handles stopping as a symptom and safety rule rather than a taper: stop and ask a doctor if ringing in the ears or loss of hearing occurs, if pain gets worse or lasts more than 10 days, or if signs of stomach bleeding appear. (Source 4)
• The one rebound phenomenon documented for salicylates is not about stopping treatment but about stopping treatment of poisoning: after intravenous sodium bicarbonate was stopped, serum salicylate rose again in 8 of 377 cases (2.1%), and only one of those patients had a recurrent symptom (tinnitus). (Source 7)
• The authors of that study concluded the rebound incidence is low and that symptoms, when they occur, are often absent or mild. (Source 8)

What goes wrong

The label itself warns that magnesium salicylate, as an NSAID, may cause severe stomach bleeding, and lists the groups in whom that chance is higher. (Source 2)

• Official position, Certainty not rated.
• Size: Not applicable (label warning)
• Who: Anyone taking the product, with named higher-risk groups.
• How long: Not applicable.
• Result: No rates are given on the label; higher-risk groups named are age 60 or older, prior stomach ulcers or bleeding problems, concurrent anticoagulant or steroid, other NSAIDs, 3 or more alcoholic drinks a day, and taking more or longer than directed.
• Funding: not stated (manufacturer label)

This product contains an NSAID, which may cause severe stomach bleeding. The chance is higher if you:

A meta-analysis of observational studies found upper gastrointestinal complication risk varies several-fold between individual NSAIDs and rises 2 to 3 times further at high daily doses; no salicylate salt was among the drugs it could pool. (Source 9)

• Meta-analysis, Low certainty.
• Size: 28 studies met the meta-analysis inclusion criteria, from 2,984 articles screened.
• Who: Users of individual NSAIDs in cohort and case-control studies, compared with non-use.
• How long: Studies published 1 January 1980 to 31 May 2011.
• Result: Pooled relative risk ranged from 1.43 (95% CI 0.65, 3.15) for aceclofenac to 18.45 (95% CI 10.99, 30.97) for azapropazone; ibuprofen 1.84 (95% CI 1.54, 2.20), naproxen 4.10 (95% CI 3.22, 5.23), piroxicam 7.43 (95% CI 5.19, 10.63)
• Funding: European Community's Seventh Framework Programme (SOS project)

Pooled RR ranged from 1.43 (95% CI 0.65, 3.15) for aceclofenac to 18.45 (95% CI 10.99, 30.97) for azapropazone.

A case-control study designed specifically to test five possible biases found a very strong association between salicylate exposure and Reye's syndrome in children, which is why salicylate labels carry a Reye's warning. (Source 10)

• Case-control study, Low certainty.
• Size: 24 case subjects and 48 matched controls.
• Who: Children with Reye's syndrome and matched controls.
• How long: Case-control, with alternate-condition control group and record review.
• Result: 88% of cases versus 17% of controls had received aspirin before Reye's syndrome onset; matched odds ratio 35 (95% confidence interval 4.2 to 288)
• Funding: not stated.

Limit of this finding: The abstract prints 'Eight-eight percent of case subjects' where it plainly means eighty-eight percent; the typo is the journal's own and is kept here unaltered. The figures are internally consistent either way (21 of 24 cases is 87.5 per cent). This study is about aspirin, not magnesium salicylate: it is recorded because it is the evidence behind the Reye's syndrome warning that every salicylate label carries.

Eight-eight percent of case subjects and only 17% of controls had received aspirin prior to the onset of Reye's syndrome (matched odds ratio, 35; 95% confidence interval, 4.2 to 288).

The magnesium salicylate label carries the same Reye's syndrome restriction as aspirin for children and teenagers with chicken pox or flu-like symptoms. (Source 2)

• Official position, Certainty not rated.
• Size: Not applicable (label warning)
• Who: Children and teenagers with or recovering from chicken pox or flu-like symptoms.
• How long: Not applicable.
• Result: No rate given; the label instructs that this group should not use the product and that behaviour change with nausea and vomiting could be an early sign of Reye's syndrome.
• Funding: not stated (manufacturer label)

Children and teenagers who have or are recovering from chicken pox or flu-like symptoms should not use this product.

Salicylate is directly ototoxic at high exposure, producing tinnitus and a reversible sensory hearing loss, and measurable changes in human auditory perception. (Source 11)

• Expert review, not systematic, Low certainty.
• Size: Not applicable (review of animal and human work)
• Who: Animal models plus human salicylate and aspirin exposure.
• How long: Acute and chronic dosing studies.
• Result: No incidence figures; the review reports frequency-dependent reductions in DPOAEs and compound action potential amplitudes, and in humans decreased word discrimination and temporal integration ability.
• Funding: not stated.

Salicylate's ototoxic properties have been well established, inducing tinnitus and a sensory hearing loss when administered in high doses.

Acute salicylate poisoning is common and the initial salicylate concentration alone did not predict who would do badly. (Source 12)

• Cohort study, Low certainty.
• Size: 48 patients met inclusion criteria out of 1,997 overdoses screened.
• Who: Adults presenting to two urban university teaching hospital emergency departments with confirmed salicylate ingestion.
• How long: Prospective cohort 2009 to 2013, in-hospital outcomes.
• Result: 20.8% had a severe outcome (acidemia pH <7.3 or bicarbonate <16 mEq/L, haemodialysis, and/or death); independent predictors were age (OR 1.13; 95% CI 1.02-1.26) and respiratory rate (OR 1.29; 95% CI 1.02-1.63); mean initial salicylate concentration 28.1 mg/dL (SD 26.6)
• Funding: not stated.

Limit of this finding: The percentages in this cohort belong to its own denominator of poisoning presentations and say nothing about the risk of taking a labelled dose. Salicylate poisoning figures must not be read as a side-effect rate for ordinary use.

However, when adjusted for salicylate concentration, only age (OR 1.13; 95% CI 1.02-1.26) and respiratory rate (OR 1.29; 95% CI 1.02-1.63) were independent predictors.

Salicylate poisoning is reported more than 20,000 times a year in the United States. (Source 13)

• Official position, Certainty not rated.
• Size: More than 20,000 exposures reported annually in the United States.
• Who: US poison centre reports.
• How long: Annual.
• Result: More than 20,000 exposures reported annually.
• Funding: not stated.

Salicylate poisoning remains a significant public health threat with more than 20,000 exposures reported annually in the United States.

Non-acetylated salicylates are usually, but not always, tolerated by people whose asthma is triggered by aspirin: 2 of 10 aspirin-sensitive asthmatic patients reacted to a non-acetylated salicylate on blinded challenge. (Source 14)

• Randomized trial, Very low certainty.
• Size: 10 aspirin-sensitive patients with asthma.
• Who: Adults with confirmed aspirin-sensitive asthma.
• How long: Double-blind placebo-controlled oral challenges with confirmatory re-challenge.
• Result: All 10 reacted to aspirin; 2 of 10 developed respiratory reactions to 2 g of salsalate, reproduced on repeat challenge; reactions were described as mild and easily treated with beta-2 agonists.
• Funding: not stated (two authors affiliated to the salsalate manufacturer per the author list)

Limit of this finding: This was a challenge study in ten patients, and two of them reacted. Two out of ten cannot pin down how common cross-reaction is; the true figure could be a good deal higher or lower. The drug challenged was salsalate, not magnesium salicylate. The authors' own wording, that non-acetylated salicylates 'may occasionally cross-react', is the right strength to take from it.

All 10 patients sustained asthmatic reactions to ASA, but only two developed respiratory reactions to 2 gm of salsalate.

A magnesium-containing oral medicine taken by older people with reduced kidney function caused severe and in one case fatal hypermagnesemia, which is the mechanism behind the kidney-disease caution on the magnesium salicylate label. (Source 5)

• Case series, Very low certainty.
• Size: 4 elderly patients.
• Who: Patients older than 65 years with constipation and renal dysfunction.
• How long: Case series; one lethal course.
• Result: 4 of 4 patients were older than 65 years with renal dysfunction and symptomatic hypermagnesemia; one died. The ingested product was magnesium oxide, not magnesium salicylate.
• Funding: not stated.

Limit of this finding: The medicine these four patients took was magnesium oxide, a laxative and antacid, not magnesium salicylate or any other salicylate. It is recorded here only because it shows what a magnesium load can do in older people whose kidneys are not clearing it, which is the reason the magnesium salicylate label asks people with kidney disease to check first. Four cases cannot give a rate: the authors' statement that this is 'more likely to develop than previously recognized' is their inference from those four, not a measured incidence.

In this report, we present the cases of four elderly patients with constipation and symptomatic hypermagnesemia caused by MgO ingestion, one of which had a lethal course.

What the evidence supports

The only use the US over-the-counter label claims for magnesium salicylate is temporary relief of minor backache pain. (Source 2)

• Official position, Certainty not rated.
• Size: One marketed product label.
• Who: Adults and children 12 years and over, per the label.
• How long: Label states not to use longer than 10 days for pain.
• Result: Label use statement: 'for the temporary relief of minor backache pain'; dose 2 caplets every 6 hours, not to exceed 8 caplets in 24 hours.
• Funding: not stated (manufacturer label)

for the temporary relief of minor backache pain

A non-acetylated salicylate closely related to magnesium salicylate did not inhibit platelet aggregation, while an equivalent salicylate dose of aspirin did. (Source 1)

• Randomized trial, Low certainty.
• Size: 12 healthy volunteers.
• Who: Healthy adult volunteers.
• How long: Two single doses 10 days apart, double blind, random order.
• Result: Single oral dose 652 mg aspirin versus 655 mg choline magnesium trisalicylate: aspirin markedly inhibited collagen-induced (p<0.005), arachidonic-acid-induced (p<0.01) and spontaneous (p<0.01) platelet aggregation; no such effects after the non-acetylated salicylate.
• Funding: not stated (product supplied as Napp Laboratories Ltd preparation in a companion paper)

Limit of this finding: The record spells out the less-than signs as 'p less than 0.005' and 'p less than 0.01'; that is how the PubMed record prints them and the printed journal almost certainly sets them as p<0.005 and p<0.01. The two doses, 652 mg of aspirin and 655 mg of the non-acetylated salicylate, differ by 3 mg because they were matched on salicylate content, not mistyped. The drug tested was choline magnesium trisalicylate, not magnesium salicylate.

Despite a comparable absorption of salicylic acid from the two drugs, ingestion of ASA resulted in a marked inhibition of platelet aggregation induced by collagen (p less than 0.005), AA (p less than 0.01) and spontaneous aggregation (p less than 0.01), whereas such effects were not observed after CMT ingestion.

The non-acetylated salicylate salsalate did not prolong bleeding time or impair platelet aggregation in healthy people or in people with haemophilia A. (Source 15)

• Randomized trial, Very low certainty.
• Size: 12 healthy subjects and 9 patients with haemophilia A.
• Who: Healthy adults and men with haemophilia A.
• How long: Not stated in the abstract.
• Result: No change in bleeding time, platelet aggregation to ADP or collagen, or ATP release to arachidonic acid in healthy subjects; no bleeding time prolongation or aggregation effect in the haemophilia A patients.
• Funding: not stated.

Limit of this finding: The source's first sentence prints 'Salsalate in a non-acetylated salicylate' where it means 'is'. That is the journal record's own typo, kept here unaltered. It does not affect the result. Note also that this was salsalate, a different salicylate from magnesium salicylate, in a few dozen people, measuring platelet laboratory tests rather than bleeding events.

Healthy subjects showed no change in bleeding time, platelet aggregation response to adenosine diphosphate (ADP) or collagen, or adenosine triphosphate (ATP) release in response to arachidonic acid as measured in an impedance whole blood lumi-aggregometer.

What the evidence does not support

A 2026 systematic review and meta-analysis of oral NSAIDs for low back pain was able to assess only six NSAIDs, none of them a salicylate salt, which is one measure of how little trial evidence exists for magnesium salicylate in its own approved use. (Source 16)

• Systematic review, Certainty not rated.
• Size: 11 randomised controlled trials, 3,784 patients.
• Who: Adults with acute or chronic low back pain with or without radiculalgia.
• How long: Trials to 31/12/2024.
• Result: Of six NSAIDs studied, only diclofenac reached 'solid evidence of efficacy' in acute low back pain; ibuprofen and naproxen were 'conclusive to be confirmed'; for the other treatments and indications the conclusion was 'lack of evidence'. Magnesium salicylate was not among the drugs assessed.
• Funding: not stated.

To assess the efficacy of naproxen, ibuprofen, ketoprofen, diclofenac, etoricoxib and celecoxib in low back pain with or without radiculalgia.

The accepted explanation for aspirin's distinctive cardiovascular benefit is irreversible acetylation of platelet cyclo-oxygenase-1, a step a non-acetylated salicylate such as magnesium salicylate cannot perform. (Source 3)

• Expert review, not systematic, Certainty not rated.
• Size: Not applicable (mechanistic review)
• Who: Not applicable.
• How long: Not applicable.
• Result: No effect estimate; the review attributes aspirin's unique effectiveness among COX-1 inhibitors to long-lasting suppression of thromboxane A2 by inactivation of platelet COX-1.
• Funding: not stated.

Limit of this finding: This is a narrative review, and the sentence quoted is the reviewers' account of the accepted mechanism rather than a new measurement. It is used here only for why aspirin's heart and stroke trials cannot be read across to a salicylate with no acetyl group. The review's wider argument about aspirin's other effects is not evidence for anything about magnesium salicylate.

Inactivation of platelet cyclooxygenase (COX)-1 by low-dose aspirin leads to long-lasting suppression of thromboxane (TX) A2 production and TXA2-mediated platelet activation and aggregation. This effect is necessary and sufficient to explain aspirin's unique (among other COX-1 inhibitors) effectiveness in preventing atherothrombosis

Where the evidence is mixed

Even among the NSAIDs that have been trialled for low back pain, the measured effect was small, which sets the ceiling on what an untested salicylate salt could plausibly deliver. (Source 17)

• Meta-analysis, Low certainty.
• Size: 11 randomised controlled trials, 3,784 patients.
• Who: 2,142 chronic and 1,642 acute low back pain.
• How long: Varied by trial.
• Result: 6 of 11 trials at low risk of bias for pain intensity, 5 at high risk; the review states the magnitude of effect was small and not clinically relevant.
• Funding: not stated.

For all the analyses, the magnitude of the effect was small and not clinically relevant.

Where the research disagrees

Whether non-acetylated salicylates such as magnesium salicylate are safe for people whose asthma is triggered by aspirin

• Stevenson and colleagues, Scripps Clinic, Double-blind placebo-controlled oral challenge in 10 aspirin-sensitive asthmatic patients: All 10 patients sustained asthmatic reactions to ASA, but only two developed respiratory reactions to 2 gm of salsalate. (Source 14)
• Nizankowska, Szczeklik and colleagues, Krakow, Double-blind placebo-controlled randomised crossover challenge study in 9 aspirin-intolerant patients: Aspirin (ASA) and other non-steroidal anti-inflammatory drugs, which are cyclooxygenase (COX) inhibitors, precipitate asthmatic attacks in ASA-intolerant patients, while sodium salicylate, hardly active on COX by itself, is well tolerated by these patients. (Source 6)

How much

• Reference intake: Magnesium salicylate is an over-the-counter product, so the dose is set by the product label rather than by a prescriber or by a nutrient reference intake. The Doan's Maximum Strength label, SPL effective 2026-04-24, states: 'adults and children 12 years and over: 2 caplets every 6 hours, not to exceed 8 caplets in 24 hours' and 'children under 12 years: do not use unless directed by a doctor'. This is the manufacturer's labelled regimen, recorded here as a position, not a recommendation. (Source 18)
• Upper limit: The label's own maximum is 8 caplets in 24 hours, each caplet containing magnesium salicylate tetrahydrate 580 mg (equivalent to 467.2 mg anhydrous magnesium salicylate) and magnesium 45 mg. The label also sets duration limits, telling the user to stop and ask a doctor if pain lasts more than 10 days or fever more than 3 days. No separate tolerable upper intake level exists because this is a drug, not a nutrient. (Source 18)
• Studied: We found no placebo-controlled trial that gave people magnesium salicylate, so no studied dose can be reported for this salt. The closest dosed human experiments used related non-acetylated salicylates: a single oral 655 mg dose of choline magnesium trisalicylate compared with 652 mg aspirin in 12 healthy volunteers. (Source 1)
• Studied: Blinded oral challenges in aspirin-sensitive asthmatic patients used 2 g of the non-acetylated salicylate salsalate. (Source 14)

A common belief, and what the research shows

The belief: Magnesium salicylate is a gentler aspirin, so it gives you aspirin's heart protection without the stomach risk.

What the research shows: Both halves of that are wrong. On the heart side, aspirin's cardiovascular effect is attributed specifically to irreversible acetylation of platelet cyclo-oxygenase-1, and a non-acetylated salicylate does not do it: in a blinded crossover in 12 volunteers at a matched salicylate dose, aspirin markedly inhibited platelet aggregation whereas the non-acetylated salicylate did not, with the authors writing that 'such effects were not observed after CMT ingestion'. On the stomach side, the magnesium salicylate label itself carries the NSAID bleeding warning: 'This product contains an NSAID, which may cause severe stomach bleeding. The chance is higher if you:' followed by a list that includes being 60 or older and drinking three or more alcoholic drinks a day.

Questions and answers

What is it?

Magnesium salicylate is the magnesium salt of salicylic acid, taken as a tablet or caplet for pain. It is classed on its US over-the-counter label as a non-steroidal anti-inflammatory drug, and the Doan's Maximum Strength label states each caplet holds magnesium salicylate tetrahydrate 580 mg, equivalent to 467.2 mg of anhydrous magnesium salicylate. It is a non-acetylated salicylate, meaning it lacks the acetyl group that aspirin carries. (Source 2)

What does it do in the body?

In the body it releases salicylate, which weakly blocks the cyclo-oxygenase enzymes that make prostaglandins, damping pain and inflammation signals. Because it has no acetyl group to hand over, it does not permanently disable the cyclo-oxygenase inside platelets. In a blinded crossover in 12 healthy volunteers, a closely related non-acetylated salicylate left platelet aggregation untouched while a matched salicylate dose of aspirin strongly suppressed it. (Source 1)

Is it good or bad for you?

It depends entirely on who is taking it and for how long. For short-term minor backache in a healthy adult the label treats it as acceptable, though we found no placebo-controlled trial supporting that use. For a child or teenager with chicken pox or flu-like symptoms it is contraindicated because of Reye's syndrome; for someone 60 or older, with a prior ulcer, on an anticoagulant or drinking heavily, the stomach-bleeding risk is raised; and for someone with reduced kidney function the magnesium load matters. The label itself says it should not be used at 20 weeks or later in pregnancy unless a doctor directs it. (Source 18)

How do you get more of it?

This is a manufactured medicine, not a nutrient, so there is no dietary route to it and no reason to seek more of it. The only sources are over-the-counter products labelled as magnesium salicylate or magnesium salicylate tetrahydrate, whose labelled regimen is 2 caplets every 6 hours for adults and children 12 and over, not exceeding 8 caplets in 24 hours. We record that as the label's position and not as advice. (Source 18)

If it is harmful, what reduces it?

Stopping the drug is what reduces it; there is no withdrawal syndrome described for it in the literature we searched. In overdose, clinical practice uses urine alkalinisation with intravenous sodium bicarbonate to pull salicylate out, and a 377-case review found that after that infusion is stopped the salicylate concentration rebounded in 2.1% of cases, with symptoms absent or mild in almost all of them. (Source 7)

Why might someone be low in it or missing it?

The question does not apply in the usual sense: nobody is deficient in magnesium salicylate, because the body does not need it and does not make it. Someone would simply not have it in their system if they have not taken a product containing it. The nearest meaningful version of the question is who should not have it, and the label answers that: it is not for children under 12 unless a doctor directs, and not for anyone allergic to salicylates. (Source 4)

Which whole foods contain it or feed it?

No whole food contains magnesium salicylate as such. Salicylates do occur naturally in plant foods, and salicylic acid and its salts are also used in cosmetics, but the magnesium salt sold as a back-pain tablet is a manufactured pharmaceutical. The label lists only pharmaceutical excipients alongside the active ingredient. (Source 18)

What happens if you do not have it?

Nothing happens: there is no deficiency state. Not taking it simply means not having whatever analgesic effect it provides, and that effect has not been quantified against placebo in any trial we found. The 2026 NSAID meta-analysis in low back pain is a fair guide to the scale of what is being forgone, and even for the NSAIDs that have been trialled it concluded the effect was small. (Source 17)

How can you test for it?

There is no test for magnesium salicylate itself in routine use. What laboratories measure is the serum salicylate concentration, which is the standard test in suspected salicylate poisoning and is reported in mg/dL or mg/L. Its limitation is well documented: in a prospective cohort of 48 adult overdoses, the initial salicylate concentration on its own did not predict who went on to a severe outcome, whereas age, respiratory rate and lactate did. (Source 12)

References

1. Scottish Medical Journal. Therapeutic potential of choline magnesium trisalicylate as an alternative to aspirin for patients with bleeding tendencies. 1987. PMID 3329766, DOI 10.1177/003693308703200603. Read the source
2. DailyMed (US National Library of Medicine), label of Dr. Reddy's Laboratories Inc. product. Doan's Maximum Strength (magnesium salicylate tetrahydrate) - Active ingredient (in each caplet), Purpose, Use and Warnings (Reye's syndrome, Allergy alert, Stomach bleeding warning) sections of the OTC Drug Facts label, each section under its own heading exactly as the label prints it, in document order; 'nonsteroidal anti-inflammatory drug' is a footnote in the SPL, printed by DailyMed as a superscript marker 1 after '(NSAID)' with the footnote text below a rule, so the marker is kept and the footnote text is given on its own line rather than run into the sentence (SPL effective 2026-04-24). 2026. Read the source
3. Journal of the American College of Cardiology. The Multifaceted Clinical Readouts of Platelet Inhibition by Low-Dose Aspirin. 2015. PMID 26139061, DOI 10.1016/j.jacc.2015.05.012. Read the source
4. DailyMed (US National Library of Medicine), label of Dr. Reddy's Laboratories Inc. product. Doan's Maximum Strength (magnesium salicylate tetrahydrate) - Do not use, Ask a doctor before use if, Ask a doctor or pharmacist before use if you are taking a prescription drug for, and Stop use and ask a doctor if sections of the OTC Drug Facts label, in document order; 'Ask a doctor before use if' and 'Stop use and ask a doctor if' carry their own heading in the SPL and are printed under it here, while the Do not use and Ask a doctor or pharmacist sections carry no heading element and are printed as the label prints them, with the heading words opening the sentence; the four signs of stomach bleeding are a nested sub-list in the SPL and are kept one to a line (SPL effective 2026-04-24). 2026. Read the source
5. CEN Case Reports. Severe hypermagnesemia induced by magnesium oxide ingestion: a case series. 2019. PMID 30136128, DOI 10.1007/s13730-018-0359-5. Read the source
6. Clinical and Experimental Allergy. Salicylate pre-treatment attenuates intensity of bronchial and nasal symptoms precipitated by aspirin in aspirin-intolerant patients. 1990. PMID 2083404, DOI 10.1111/j.1365-2222.1990.tb02703.x. Read the source
7. Clinical Toxicology. Incidence of rebound salicylate toxicity following cessation of urine alkalinization (Results section of the abstract). 2023. PMID 37427892, DOI 10.1080/15563650.2023.2227998. Read the source
8. Clinical Toxicology. Incidence of rebound salicylate toxicity following cessation of urine alkalinization (Conclusions section of the abstract). 2023. PMID 37427892, DOI 10.1080/15563650.2023.2227998. Read the source
9. Drug Safety. Individual NSAIDs and upper gastrointestinal complications: a systematic review and meta-analysis of observational studies (the SOS project) (the complete Results section of the abstract). 2012. PMID 23137151, DOI 10.2165/11633470-000000000-00000. Read the source
10. JAMA. New epidemiologic evidence confirming that bias does not explain the aspirin/Reye's syndrome association. 1989. PMID 2704111, DOI 10.1001/jama.1989.03420170061031. Read the source
11. Acta Otorhinolaryngologica Italica. Review of salicylate-induced hearing loss, neurotoxicity, tinnitus and neuropathophysiology. 2014. PMID 24843217. Read the source
12. Clinical Toxicology. Acute salicylate poisoning: risk factors for severe outcome (Results section of the abstract). 2017. PMID 28064509, DOI 10.1080/15563650.2016.1271127. Read the source
13. Clinical Toxicology. Acute salicylate poisoning: risk factors for severe outcome (Context section of the abstract, which is one sentence). 2017. PMID 28064509, DOI 10.1080/15563650.2016.1271127. Read the source
14. The Journal of Allergy and Clinical Immunology. Salsalate cross-sensitivity in aspirin-sensitive patients with asthma. 1990. PMID 2229840, DOI 10.1016/s0091-6749(05)80179-4. Read the source
15. Thrombosis Research. Hemostatic effects of salsalate in normal subjects and patients with hemophilia A. 1991. PMID 2020937, DOI 10.1016/0049-3848(91)90165-s. Read the source
16. Therapie. Efficacy of celecoxib, diclofenac, etoricoxib, ibuprofen, ketoprofen and naproxen in low back pain with or without nerve root pain: Systematic review of literature and meta-analysis of randomized controlled trials (Objectives section of the abstract, which is one sentence). 2026. PMID 42135072, DOI 10.1016/j.therap.2026.04.003. Read the source
17. Therapie. Efficacy of celecoxib, diclofenac, etoricoxib, ibuprofen, ketoprofen and naproxen in low back pain with or without nerve root pain: Systematic review of literature and meta-analysis of randomized controlled trials (Discussion section of the abstract). 2026. PMID 42135072, DOI 10.1016/j.therap.2026.04.003. Read the source
18. DailyMed (US National Library of Medicine), label of Dr. Reddy's Laboratories Inc. product. Doan's Maximum Strength (magnesium salicylate tetrahydrate) - pregnancy and breast-feeding warning, keep-out-of-reach-of-children warning, Directions, Other information, Inactive ingredients and Questions or comments? sections of the OTC Drug Facts label, in document order; Directions, Other information, Inactive ingredients and Questions or comments? carry their own heading in the SPL and are printed under it here, while the pregnancy and keep-out-of-reach sections carry no heading element and are printed as the continuous sentences the label prints (SPL effective 2026-04-24). 2026. Read the source