Goldenseal

Supplements · Immune & Antimicrobial Herbs · Supplement, Typed Supps

A woodland root long used in folk medicine for infections, now more notable for its drug interactions than proven benefits.

Stage by stage

Intake (Capsule, tincture, or tea): Often combined with echinacea in immune formulas.
Small intestine (Absorbed): Berberine and hydrastine absorbed, also inhibiting drug transporters here.
Liver (Metabolized): Inhibits CYP450 enzymes that process many prescription drugs.
Bloodstream (Circulates): Alkaloids circulate systemically; drug-interaction risk is the best-documented effect.

What the evidence supports

Preventing or treating colds and upper respiratory infections — insufficient evidence. Despite widespread popularity, often combined with echinacea in 'cold formulas,' there is little to no rigorous human trial evidence that goldenseal or its main alkaloid berberine treats or shortens respiratory infections; most support is traditional use and in vitro antimicrobial activity, not human trials.
Evidence on Drug interactions via liver enzyme and transporter inhibition — moderate evidence. Goldenseal measurably inhibits CYP3A4, CYP2D6, and probably CYP2C9. An NCCIH-funded study found it reduced metformin blood levels by roughly 20% at typical low-to-moderate doses, though a larger follow-up crossover trial found this effect shrank to negligible at high metformin doses — a real, documented, dose-dependent interaction.
Evidence on Newborn and infant jaundice risk from berberine — moderate evidence. Berberine, goldenseal's major alkaloid, can displace bilirubin from albumin and worsen jaundice in newborns, with a risk of kernicterus — this is why goldenseal is specifically contraindicated in pregnancy, breastfeeding, and infancy.

Typical dose

Products vary widely: 250–500mg of standardized extract (8–12% alkaloids) up to three times daily, or 4–6g of powdered root and rhizome daily — but there's no dose backed by solid efficacy trials.

Upper limit: No established UL; long-term safety data are lacking, and traditional-use guidance generally cautions against continuous use beyond a few weeks.

Timing

No validated efficacy dosing exists; avoid combining with prescription medications without medical guidance.

Time to effect

Unclear: No solid clinical trial evidence establishes a time-to-effect for any proposed infection-fighting benefit.

Common myth

“Goldenseal is a natural antibiotic.” In reality: Its alkaloid berberine kills bacteria in lab dishes, but that hasn’t been shown to translate into a proven infection-fighting benefit in people — its clearest documented effect is altering how the body processes other medications.