Herb & supplement monograph

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

But these pages have grown well beyond that into a full monograph — what Boldo 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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Boldo 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 Boldo drug interaction is modest for most people, though a few closely monitored medicines deserve real caution. None of the listed interactions are rated major, but all are graded moderate, and nearly all rest on limited or theoretical evidence.

Interactions deserving the most attention

The best-documented concern is lithium: boldo may act as a mild diuretic, which could reduce how the body clears lithium and raise its levels. Tacrolimus also stands out, since one transplant patient with long-stable levels saw them drop below target while taking boldo, a change that could risk rejection. People on warfarin or other blood thinners should be watchful too, as one case tied a boldo and fenugreek combination to a higher INR. Boldo itself has been linked to liver injury, so combining it with other medicines that can stress the liver adds to that risk.

What the rest of the list means

The long list mostly reflects broad drug groups, not proven harm with each individual medicine. Most of these concerns come from lab or animal research or single case reports, and for many combinations a meaningful effect has not been confirmed in people.

Check your medications against Boldo

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

Interaction report

Drugs that interact with Boldo

484 medications have a known interaction with Boldo, 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 Boldo using our pharmacist-reviewed interaction data.

AI summaries are generated from our Boldo 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 Boldo 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 Boldo affects

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

All 5 drug categories Boldo interacts with

Anticoagulant/antiplatelet DrugsHepatotoxic DrugsLithiumTacrolimus (prograf)Warfarin (coumadin)

Anticoagulant/Antiplatelet Drugs

Theoretically, taking boldo with anticoagulant/antiplatelet drugs might increase the risk of bleeding.
Animal and in vitro research shows that boldine, a constituent of boldo, has antiplatelet activity. In one case report, an adult taking a combination of boldo and fenugreek with warfarin experienced an increase in international normalized ratio (INR); however, it is unclear if this effect was due to boldo, fenugreek, the combination, or another factor.

Likelihood Possible Evidence D

Hepatotoxic Drugs

Theoretically, taking boldo with hepatotoxic drugs might increase the risk of hepatic injury and disease.
Boldo leaf contains ascaridole, a known liver toxin. Many cases of hepatotoxicity, including elevated liver transaminase levels and jaundice, have been reported in patients taking boldo.

Likelihood Possible Evidence D

Lithium

Theoretically, taking boldo with lithium might increase the levels and clinical effects of lithium.
Boldo is believed to have diuretic effects. Theoretically, these diuretic effects might reduce the excretion of lithium. The dose of lithium might need to be decreased.

Likelihood Probable Evidence D

Tacrolimus (Prograf)

Taking boldo with tacrolimus may decrease the levels and clinical effects of tacrolimus, potentially increasing the risk of transplant rejection.
In one case report, a patient with a long-term history of stable tacrolimus levels developed subtherapeutic levels after taking boldo 300 mg twice daily orally for several weeks. Tacrolimus levels returned to normal after discontinuing boldo. However, the mechanism of this interaction is unclear.

Likelihood Possible Evidence D

Warfarin (Coumadin)

A combination of boldo and fenugreek was thought to be associated with an increased international normalized ratio (INR) in a female on warfarin. It is not clear if boldo, fenugreek, or the combination played a role in this interaction. Therefore, boldo may have additive effects with warfarin.

Likelihood Possible Evidence D

Monograph

Boldo: Uses, Safety & Side Effects

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

The bottom line

Boldo is a South American shrub whose leaves are traditionally used for digestive and gallbladder complaints, but good human evidence is very limited. The leaves and oil contain ascaridole, which can be toxic to the liver, so only ascaridole-free products should be used and only for short periods. Talk to your pharmacist or doctor before trying it, and avoid it during pregnancy and breastfeeding.

Scientific name: Peumus boldus
Family: Monimiaceae
Part used: Leaves and essential oil
Common forms: Tea, dried leaf, tincture, capsules, essential oil

People commonly use it for

Indigestion and bloating
Mild constipation
Liver and gallbladder support
Appetite stimulation
Urinary complaints

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

Safety at a glance

OverallUse caution

May be used short-term in low doses, but the ascaridole in the leaf and oil can harm the liver.

PregnancyPossibly Unsafe

When used orally in medicinal amounts. In animals, boldo and the constituent boldine have abortive and teratogenic effects. Also, the ascaridole const...

Read the full pregnancy detail

BreastfeedingPossibly Unsafe

When used orally in medicinal amounts. In animals, boldo and the constituent boldine have abortive and teratogenic effects. Also, the ascaridole const...

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

Boldo (Peumus boldus) is a small evergreen tree or shrub native to Chile and other parts of South America. It has small, leathery, dark green leaves with a strong, distinctive aroma. The leaves are the part used most often.

In its native region, boldo leaves are used both as a cooking herb and in traditional medicine. People most commonly take it as a tea or in capsules and tinctures for stomach and gallbladder complaints. The essential oil is much more concentrated and is generally not recommended for self-use.

How it works

The leaves contain an alkaloid called boldine, along with flavonoids and an essential oil. Boldine is thought to act as an antioxidant and may help the liver make and release bile, which could explain its traditional use for digestion and gallbladder complaints.

The essential oil also contains ascaridole, a compound that has been used as a wormer but can be toxic, especially to the liver. Most of these proposed effects come from test-tube and animal studies, so it is not clear how well they apply to people taking the herb.

Effectiveness

Does Boldo work?

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

Evidence overview · 5 uses evaluated

5 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.

For Boldo, current evidence isn’t strong enough to rate any specific use. The conditions it has been studied for are listed below.

Also studied for 5 conditions — evidence insufficient to rate

Insufficient Reliable Evidence To Rate Benign prostatic hyperplasia (BPH)