Herb & supplement monograph

Bilberry Drug Interactions, Uses, Effectiveness, Safety & More

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS ·Updated July 2026

What is this page for?

First and foremost: how Bilberry interacts with medications. The heart of this page is the interaction list — every drug Bilberry is known to interact with, and how serious each one is.

But these pages have grown well beyond that into a full monograph — what Bilberry is, what people use it for and how strong the evidence is, its safety and side effects, and answers to the questions we’re asked most — written and reviewed by the clinical staff at HelloPharmacist. It’s educational information from our licensed clinical databases, not medical advice, and we don’t sell or endorse products. Our editorial policy

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On this page

Bilberry Drug Interactions: The Bottom Line

From the HelloPharmacist Editorial Team · Updated July 2026

Based on the available evidence, the overall risk of a clinically significant Bilberry drug interaction appears low for most people. Every listed interaction is rated moderate rather than major, and none has been well documented in humans, so the concerns are largely theoretical.

Interactions deserving the most attention

The combinations most worth watching involve blood thinners such as anticoagulant and antiplatelet drugs, since bilberry extracts may reduce platelet clumping and could add to bleeding risk. Diabetes medications also deserve attention because one small human study found bilberry fruit extract lowered blood sugar, which could add to the effect of these drugs. There is also lab research suggesting bilberry might reduce how well the cancer drug erlotinib works, though this has not been seen in people.

What the rest of the list means

Bilberry's long list of interacting medications does not mean each combination is harmful. Most entries come from lab or animal research, including possible effects on an enzyme the body uses to clear certain medications, where results were inconsistent and no effect has been shown in humans. In many cases, a predicted effect has simply never been confirmed in people.

Check your medications against Bilberry

Based on HelloPharmacist’s Bilberry interaction data and reviewed under our editorial standards.

Interaction report

Drugs that interact with Bilberry

275 medications have a known interaction with Bilberry, graded by severity. Select any drug for the full evidence-based detail.

Don’t want to scroll the list? Just ask.

Tell us the medications you take and we’ll check each one against Bilberry using our pharmacist-reviewed interaction data.

AI summaries are generated from our Bilberry interaction data for education only — always confirm with your pharmacist. How we use AI

2,830 drugs

Read The List Like a Pharmacist

What Severity, Likelihood & Evidence Mean

Severity — How Serious It Can Be

Major. Clinically significant; generally best avoided, or used only under direct professional supervision.
Moderate. May need monitoring, a dose adjustment, or separating the times you take each one.
Minor. Generally not clinically significant, but still worth noting and mentioning to your pharmacist.
No known interaction. Checked against our sources with nothing documented — not the same as proven safety.

Likelihood — How Well It’s Documented

Likely. Well-controlled human studies have demonstrated the likely existence of this interaction
Probable. Interaction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
Possible. Interaction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists
Unlikely. Interaction has been demonstrated in animal or in lab research but has been shown not to occur in humans.

Where This Data Comes From

Interaction records are evidence-graded and sourced from the Natural Medicines database (TRC Healthcare), the same reference used by pharmacists and hospitals.
Each drug listed above links to the full report for that exact Bilberry combination — clinical detail, likelihood, evidence level, and citations.
Content is reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

The big picture

The kinds of drugs Bilberry affects

Every type of medication (drug category) Bilberry is known to interact with. Open any category for the detail — or search your exact drug in the checker above.

All 4 drug categories Bilberry interacts with

Anticoagulant/antiplatelet DrugsAntidiabetes DrugsCytochrome P450 2e1 (cyp2e1) SubstratesErlotinib (tarceva)

Anticoagulant/Antiplatelet Drugs

Theoretically, bilberry fruit extract might increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs.
In vitro, animal, and clinical research suggest that anthocyanidin extracts from bilberry can inhibit platelet aggregation.

Likelihood Possible Evidence D

Antidiabetes Drugs

Theoretically, bilberry leaf or fruit extract may increase the risk of hypoglycemia when taken with antidiabetes drugs.
Animal research suggests that bilberry leaf extract might have blood glucose-lowering activity. Also, one small clinical trial in patients with type 2 diabetes shows that taking bilberry fruit extract 470 mg as a single dose prior to an oral glucose tolerance test lowers plasma glucose levels when compared with placebo.

Likelihood Possible Evidence D

Cytochrome P450 2E1 (Cyp2E1) Substrates

Theoretically, bilberry fruit extract might decrease levels of drugs metabolized by CYP2E1.
Animal research shows that exposure to small concentrations of bilberry extract in drinking water for around one month increased CYP2E1 activity by 31%. However, exposure over a 2-month period did not increase CYP2E1 activity. This effect has not been reported in humans.

Likelihood Possible Evidence D

Erlotinib (Tarceva)

Theoretically, bilberry fruit extract might reduce the efficacy of erlotinib.
In vitro research suggests that bilberry fruit extract and its constituents, delphinidin and delphinidin-3-O-glucoside, inhibit the activity of erlotinib. This interaction has not been reported in humans.

Likelihood Possible Evidence D

Monograph

Bilberry: Uses, Safety & Side Effects

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Reviewed July 2026 ·

The bottom line

Bilberry is a blueberry-like fruit rich in antioxidant plant compounds called anthocyanins, and it has a long history of traditional use for eye health, circulation, and mild diarrhea. While it is generally well tolerated as a food and supplement, strong scientific proof for most health claims is limited. Talk with your pharmacist or doctor before using bilberry supplements, especially if you are pregnant, breastfeeding, or have a health condition.

Scientific name: Vaccinium myrtillus
Family: Ericaceae
Part used: Berries (fruit) and sometimes leaves
Common forms: Capsules, tablets, standardized extracts, dried berries, tea, liquid extracts

People commonly use it for

Eye and vision health
Antioxidant support
Diarrhea and digestive upset
Circulation and vein health
Blood sugar support

Popular and traditional uses — not proof it works. See “Uses & effectiveness” below for the evidence.

Safety at a glance

OverallUse caution

Bilberry fruit is generally safe as food, but supplement evidence and long-term safety are limited.

PregnancyLikely Safe

When used orally in the amounts commonly found in foods. However, there is insufficient reliable information available about the safety of bilberry wh...

Read the full pregnancy detail

BreastfeedingLikely Safe

When used orally in the amounts commonly found in foods. However, there is insufficient reliable information available about the safety of bilberry wh...

Read the full breastfeeding detail

Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center). Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

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Overview

Bilberry (Vaccinium myrtillus) is a small, low-growing shrub that produces dark purple-blue berries that look much like blueberries. It is native to parts of Europe, northern North America, and Canada, and grows in woodlands and on heaths.

The berries are eaten as food and are also dried or made into extracts for supplements. Bilberry is naturally high in antioxidant plant pigments called anthocyanins, which give the fruit its deep color. It also contains vitamins such as vitamin C.

People have used bilberry in traditional medicine for many years, most famously for eye and vision support, but also for diarrhea, circulation problems, and general antioxidant benefits.

How it works

The main active compounds in bilberry are anthocyanins and other flavonoids. These act as antioxidants, meaning they may help protect cells from a type of damage called oxidative stress.

Researchers believe these compounds may help support small blood vessels and improve blood flow, which is part of why bilberry has been studied for eye and circulation health. The dried fruit also contains tannins, which can have a drying, anti-diarrhea effect in the gut.

It is important to know that many of these proposed mechanisms come from laboratory and animal studies, and they do not always translate into clear benefits in people.

Effectiveness

Does Bilberry work?

Here’s what the research actually shows for each use — graded by Natural Medicines and reviewed by Dr. Brian Staiger, PharmD.

Evidence overview · 26 uses evaluated

1 Leans ineffective 25 Insufficient evidence

How to read these evidence grades

Natural Medicines’ 7-point scale. We show each rating’s label word-for-word.

1EffectiveStrong, consistent evidence it works.

2Likely EffectiveGood evidence, though not yet conclusive.

3Possibly EffectiveSome evidence suggests a benefit.

4Possibly IneffectiveSome evidence it may not help.

5Likely IneffectiveFairly strong evidence it doesn’t help.

6IneffectiveStrong evidence it doesn’t work.

7Insufficient Reliable Evidence to RateToo little research to say either way.

Possibly Ineffective Night vision