Bilberry

What it is

Bilberry is the fruit of Vaccinium myrtillus, a relative of the blueberry. Supplements are extracts of the fruit concentrated for anthocyanosides (anthocyanins), the purple pigments. It is used in traditional medicine for eye disorders and vision.

What the research says

The best-known claim, better night vision, is not supported: a systematic review found the four most recent randomised trials negative, and positive results came from weaker studies. A 2025 meta-analysis of 11 small trials found no significant effect on blood pressure, fasting glucose, weight or inflammation markers, and only a borderline drop in HbA1c. One industry-linked Japanese trial reported less screen-related eye fatigue. Harms reported include bleeding when combined with blood thinners, and commercial extracts have repeatedly been found adulterated.

Evidence grade: Limited evidence.

What goes wrong

In the same trial minor adverse events occurred at similar rates on bilberry and placebo. (Source 1)

• Randomized trial, Low certainty.
• Size: 80 completers.
• Who: office workers.
• How long: 8 weeks.
• Result: 11.6% bilberry vs 13.5% placebo reported minor adverse events; no severe events.
• Funding: industry-funded.

Five of 43 subjects (11.6%) in the BE group, and 5 of 37 subjects (13.5%) in the placebo group reported a collective total of 15 minor adverse events

A 2025 review of anticoagulant interactions states bilberry may affect platelet aggregation and increase bleeding risk with warfarin. (Source 2)

• Systematic review, Very low certainty.
• Size: not applicable.
• Who: patients on oral anticoagulants.
• How long: not applicable.
• Result: not quantified.
• Funding: not stated.

it may affect platelet aggregation, potentially increasing the risk of severe bleeding in patients on anticoagulants such as warfarin

A case report describes rectal bleeding and blood in the urine in a 77-year-old man taking bilberry with an anticoagulant. (Source 3)

• Case report, Very low certainty.
• Size: 1 patient.
• Who: 77-year-old man with a history of hypertension and stroke, taking an anticoagulant.
• How long: long-term bilberry use.
• Result: bleeding event.
• Funding: not stated.

Concomitant bilberry use was associated with rectal bleeding and hematuria in a 77-year-old man

Mark Blumenthal of the American Botanical Council, as quoted by the trade news site NutraIngredients in 2012, said some bilberry extracts on the market are priced so low they are almost certainly adulterated, with elderberry, Chinese mulberry, red dye No. 2, charcoal and black rice or soybean-hull anthocyanins named as adulterants. (Source 4)

• Official position, Certainty not rated.
• Size: not applicable.
• Who: commercial extracts.
• How long: not applicable.
• Result: not quantified.
• Funding: not applicable (expert comment reported in trade press)

Extracts are available in the market that are priced so low that it is practically impossible for them not of have been adulterated.

What the evidence supports

An 8-week Japanese RCT in office workers, conducted by the supplement maker, reported that bilberry extract significantly lessened a screen-induced drop in critical flicker fusion (a measure of eye fatigue) compared with placebo, but did not improve near-point accommodation. (Source 1)

• Randomized trial, Low certainty.
• Size: 88 enrolled, 80 completed (43 bilberry, 37 placebo)
• Who: office workers aged 20-40 using video display terminals.
• How long: 8 weeks.
• Result: CFF reduction alleviated (95% CI 0.10-1.60; p=0.023); NPA not improved.
• Funding: industry-funded.

The VDT load-induced reduction in CFF was alleviated after 8 weeks of BE supplementation (95% confidence interval, 0.10–1.60; p=0.023), in contrast to placebo supplementation, while NPA variation was not.

What the evidence does not support

A systematic review of 12 placebo-controlled trials found bilberry anthocyanosides do not improve normal night vision; the four most recent RCTs were negative. (Source 5)

• Systematic review, Low certainty.
• Size: 12 placebo-controlled trials (of 30 identified)
• Who: mostly healthy people with normal or above-average eyesight.
• How long: varied.
• Result: 4 most recent RCTs negative; 1 RCT and 7 non-randomised trials positive.
• Funding: independent (not stated)

The hypothesis that V. myrtillus anthocyanosides improves normal night vision is not supported by evidence from rigorous clinical studies.

The same review found positive night-vision results came from methodologically weaker trials, and no rigorous research exists in people with eye disease. (Source 5)

• Systematic review, Very low certainty.
• Size: 12 trials.
• Who: healthy subjects in 11 of 12 trials.
• How long: varied.
• Result: not pooled.
• Funding: not stated.

Negative outcome was associated with more rigorous methodology but also with lower dose level and extracts from geographically distinct sources

A 2025 meta-analysis of bilberry trials found no significant effect on fasting glucose, total cholesterol, triglycerides, blood pressure, body weight or inflammatory markers. (Source 6)

• Meta-analysis, Low certainty.
• Size: 409 people in 11 RCTs (8 meta-analysed)
• Who: adults.
• How long: at least 1 week.
• Result: FBG WMD -0.08 mmol/L (95% CI -0.22 to 0.07, p=0.30); SBP WMD -2.75 mmHg (p=0.13); DBP WMD -1.00 mmHg (p=0.59)
• Funding: not stated.

Limit of this finding: The abstract of this meta-analysis has internal problems. Its conclusion says bilberry 'may have beneficial effects on HbA1c and TG', but its own pooled results for HbA1c (p = 0.06) and triglycerides (p = 0.62) were not statistically significant; the triglyceride signal came only from small subgroups (crossover trials and trials of 4 weeks or less). The HbA1c figure of -1.63 percentage points is far larger than would be plausible for a berry extract and may be an error. LDL cholesterol went up slightly (+0.07 mmol/L), which is not a benefit, although the abstract lists it without comment. Several confidence intervals are printed with % signs that do not match their units. A reader should take this review as showing no proven effect of bilberry on blood sugar, blood fats, blood pressure or inflammation, and should not treat the HbA1c or triglyceride results as established benefits.

resulted in a non-significant decrease in FBG (WMD: -0.08 mmol/L, 95% CI: -0.22 to 0.07, p = 0.30)

In that meta-analysis the pooled HbA1c reduction across three trials was not statistically significant (p = 0.06), and the authors called for high-quality trials. (Source 6)

• Meta-analysis, Low certainty.
• Size: 3 RCTs for HbA1c.
• Who: adults.
• How long: varied.
• Result: HbA1c WMD -1.63% (95% CI -3.36% to 0.11%, p=0.06)
• Funding: not stated.

Limit of this finding: The abstract of this meta-analysis has internal problems. Its conclusion says bilberry 'may have beneficial effects on HbA1c and TG', but its own pooled results for HbA1c (p = 0.06) and triglycerides (p = 0.62) were not statistically significant; the triglyceride signal came only from small subgroups (crossover trials and trials of 4 weeks or less). The HbA1c figure of -1.63 percentage points is far larger than would be plausible for a berry extract and may be an error. LDL cholesterol went up slightly (+0.07 mmol/L), which is not a benefit, although the abstract lists it without comment. Several confidence intervals are printed with % signs that do not match their units. A reader should take this review as showing no proven effect of bilberry on blood sugar, blood fats, blood pressure or inflammation, and should not treat the HbA1c or triglyceride results as established benefits.

For HbA1c, the meta-analysis of three RCTs showed a marginally significant reduction (WMD: -1.63%, 95% CI: -3.36% to 0.11%, p = 0.06).

Long-term trials in the meta-analysis showed LDL cholesterol rose slightly with bilberry rather than fell. (Source 6)

• Meta-analysis, Low certainty.
• Size: 5 RCTs.
• Who: adults.
• How long: long-term (varied)
• Result: LDL WMD +0.07 mmol/L (95% CI 0.01 to 0.14, p=0.01)
• Funding: not stated.

Limit of this finding: The abstract of this meta-analysis has internal problems. Its conclusion says bilberry 'may have beneficial effects on HbA1c and TG', but its own pooled results for HbA1c (p = 0.06) and triglycerides (p = 0.62) were not statistically significant; the triglyceride signal came only from small subgroups (crossover trials and trials of 4 weeks or less). The HbA1c figure of -1.63 percentage points is far larger than would be plausible for a berry extract and may be an error. LDL cholesterol went up slightly (+0.07 mmol/L), which is not a benefit, although the abstract lists it without comment. Several confidence intervals are printed with % signs that do not match their units. A reader should take this review as showing no proven effect of bilberry on blood sugar, blood fats, blood pressure or inflammation, and should not treat the HbA1c or triglyceride results as established benefits.

revealed a significant change in LDL following bilberry supplementation (WMD: 0.07 mmol/L, 95% CI: 0.01%-0.14%, p = 0.01)

Where the research disagrees

Whether bilberry improves night vision

• Canter and Ernst 2004, systematic review of 12 placebo-controlled trials: The hypothesis that V. myrtillus anthocyanosides improves normal night vision is not supported by evidence from rigorous clinical studies. (Source 5)
• Older trials within that review, RCT and non-randomised controlled trials: A fifth RCT and 7 non-randomized controlled trials reported positive effects on outcome measures relevant to night vision. (Source 5)

How much

• Reference intake: No RDA or AI exists; bilberry is not an essential nutrient. Memorial Sloan Kettering (2023) notes clinical data for its traditional uses are mixed or lacking. (Source 3)
• Upper limit: No tolerable upper intake level has been set by any body in the sources we reached. (Source 6)
• Studied: 480 mg/day bilberry extract for 8 weeks (Ozawa 2015). (Source 1)

A common belief, and what the research shows

The belief: Bilberry improves night vision (a claim popularly linked to WWII pilots).

What the research shows: A systematic review concluded: "The hypothesis that V. myrtillus anthocyanosides improves normal night vision is not supported by evidence from rigorous clinical studies."

Questions and answers

What is it?

Bilberry is a small dark berry related to the blueberry. Supplements are fruit extracts concentrated for anthocyanosides, the purple pigments, and are traditionally used for the eyes. (Source 3)

What does it do in the body?

Rigorous trials do not show better night vision. Pooled trials show no clear effect on blood sugar, cholesterol, blood pressure or inflammation; the HbA1c drop did not reach statistical significance (p = 0.06). One industry-conducted trial reported less eye fatigue from screen use. (Source 6)

Is it good or bad for you?

In trials it caused mostly minor side effects, at rates similar to placebo. The main risk is bleeding when combined with blood thinners such as warfarin. Benefits are unproven. (Source 2)

How do you get more of it?

It comes from the fruit or from capsule extracts. The trials we found gave 480 mg a day of extract. Mark Blumenthal of the American Botanical Council, as quoted by NutraIngredients in 2012, said some commercial extracts have been adulterated with cheaper anthocyanin sources or dyes. (Source 4)

If it is harmful, what reduces it?

Does not apply, because it is not something the body needs to clear. The bleeding reports involved people who were also taking blood thinners. (Source 3)

Why might someone be low in it or missing it?

Does not apply. Bilberry is not an essential nutrient, so there is no deficiency state to be low in. (Source 6)

We searched: Canter 2004 systematic review, 2025 cardiometabolic meta-analysis, MSKCC monograph; none describe a deficiency.

Which whole foods contain it or feed it?

The whole food is the bilberry fruit itself. The sources we reached did not give anthocyanin amounts for whole bilberries versus other berries. (Source 3)

We searched: Canter 2004, 2025 meta-analysis, MSKCC bilberry monograph.

What happens if you do not have it?

Nothing is known to happen. Bilberry is not essential, and no deficiency effects are described. (Source 6)

We searched: Canter 2004; 2025 meta-analysis; MSKCC monograph.

How can you test for it?

We found no clinical test for bilberry or anthocyanin status in the literature we searched. (Source 6)

We searched: Canter 2004; 2025 meta-analysis; Ozawa 2015 RCT.

References

1. The Journal of Nutrition, Health and Aging. Bilberry extract supplementation for preventing eye fatigue in video display terminal workers. 2015. PMID 25923485. Read the source
2. Scientia Pharmaceutica. Risks of Oral Anticoagulants: Interactions with Drugs and Medicinal Plants. 2025. Read the source
3. Memorial Sloan Kettering Cancer Center. Bilberry Fruit (About Herbs), last updated March 17, 2023. 2023. Read the source
4. NutraIngredients. ABC bilberry article seeks to close door on adulteration (NutraIngredients news report quoting Mark Blumenthal of the American Botanical Council on the Foster and Blumenthal HerbalGram review, November 2012). 2012. Read the source
5. Survey of Ophthalmology (abstract via NCBI Bookshelf DARE record). Anthocyanosides of Vaccinium myrtillus (bilberry) for night vision: a systematic review of placebo-controlled trials. 2004. PMID 14711439. Read the source
6. Phytotherapy Research. Investigating the Effects of Vaccinium myrtillus Supplementation on Cardiometabolic Indices: A Systematic Review and Meta-Analysis. 2025. PMID 40751398, DOI 10.1002/ptr.70054. Read the source