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Limited evidenceMen's health

Stinging Nettle

Nettle root produced a statistically significant but clinically trivial improvement in prostate symptom scores in its largest trial, with no change in urine flow or residual volume. The leaf's allergy and joint claims rest on single small studies that were never replicated.

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What the science says

  • Benign prostatic hyperplasia symptoms Limited evidence

    In a 12-month randomised trial of 246 men, 459 mg/day of nettle root dry extract lowered IPSS from 18.7 to 13.0 versus 18.5 to 13.8 on placebo (p = 0.023) — a difference of well under one point on a 35-point scale. Peak urinary flow and residual urine volume did not differ significantly from placebo.

  • Allergic rhinitis Limited evidence

    The frequently cited evidence is a single 1990 trial of 98 patients given 600 mg/day of freeze-dried nettle leaf for one week, which found it rated moderately better than placebo on global assessment only. It has not been replicated in 35 years.

  • Joint pain, blood sugar and blood pressure Limited evidence

    These claims come from preclinical work and a few very small trials, often using combination products or topical application. There is no adequate human evidence that oral nettle helps arthritis, glycaemic control or hypertension.

Dosage & safety

Studied doseRoot (for urinary symptoms): 360-600 mg/day of standardised dry extract, often 120 mg twice daily, for 3-12 months. Leaf (for rhinitis): 600 mg of freeze-dried leaf, up to three times daily. Root and leaf are chemically distinct products used for different purposes — check which one you are buying.
SafetyGenerally mild: gastrointestinal upset, sweating and occasional rash. Nettle has diuretic and mild blood-pressure- and glucose-lowering effects, so it can add to the action of diuretics, antihypertensives and diabetes medication, and may raise lithium levels through fluid shifts. Nettle leaf is high in vitamin K and may reduce the effect of warfarin. Avoid in pregnancy (uterine stimulant activity reported). Handling the raw plant causes contact urticaria. Nettle root is not a substitute for proper assessment — obstructive urinary symptoms need a prostate evaluation.

How to take it

TimingRoot twice daily for urinary symptoms; leaf up to three times daily during allergy season.
With food?With food to avoid stomach upset.
Worth knowingRoot and leaf are chemically different products — root for prostate and urinary symptoms, leaf for rhinitis — and buying the wrong one is the commonest mistake here.

Interactions

With medications

  • warfarin

    Nettle leaf is high in vitamin K and can reduce warfarin's effect. avoid the leaf, or keep intake constant and monitor INR

  • antihypertensives and diuretics

    Nettle has diuretic and mild blood-pressure-lowering effects that add to theirs. monitor blood pressure and hydration when starting

  • lithium

    The diuretic effect can reduce lithium clearance and raise levels. do not combine without monitoring lithium levels

  • insulin and sulfonylureas

    Mild glucose-lowering effect can add to theirs. monitor glucose when starting

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does stinging nettle root help an enlarged prostate?

Only trivially: in a 12-month trial of 246 men, nettle root cut prostate symptom scores by well under one point more than placebo on a 35-point scale, with no change in urine flow. The evidence is limited.

Does stinging nettle help allergies?

The evidence is limited to one 1990 trial of 98 patients, where freeze-dried nettle leaf rated moderately better than placebo on global assessment only. That stinging nettle result has not been replicated in 35 years.

Should I buy nettle root or nettle leaf?

They are different products: stinging nettle root is used for prostate and urinary symptoms at 360-600 mg/day, and nettle leaf for rhinitis at 600 mg up to three times daily. Buying the wrong one is the commonest mistake.

Does stinging nettle interact with medications?

Stinging nettle leaf is high in vitamin K and can reduce warfarin's effect. Nettle's diuretic effect can raise lithium levels and add to blood pressure and diabetes medication, so monitor when starting.

Scientific references

Where to buy

Swanson Vitamins, Stinging Nettle Root, 500 mg, 100 Capsules

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