Nettle tea: dangers, contraindications and when to avoid it

The short answer

No, nettle tea is not dangerous for a healthy adult at the usual doses and over a few weeks. The European Medicines Agency (EMA) recognises the traditional use of nettle leaf to relieve minor joint pain and to increase urine volume. It contraindicates it in severe heart or kidney disease where fluids must be limited, and advises against it during pregnancy, breastfeeding and under 12 years, because of a lack of data. No drug interaction has been reported, but nettle leaves eaten as a soup are very rich in vitamin K, something to know if you take anticoagulants.

This article is for information only and does not replace medical advice. If you have a chronic condition or are on treatment, talk to your doctor or pharmacist.

What the European Medicines Agency says

The EMA’s Committee on Herbal Medicinal Products has published a monograph on nettle leaf, Urtica dioica and Urtica urens. It is the European reference for herbal teas and extracts sold as traditional medicines. Its key points:

Point	What the monograph says
Traditional uses	relief of minor joint pain; increase in urine volume to « flush » the urinary tract, as an adjunct, in minor urinary complaints
Dose as tea	2 to 4 g of leaves per cup, 3 to 6 times a day, i.e. 8 to 12 g a day
Duration	4 weeks at most for joint pain, 2 to 4 weeks for urinary use
Contraindications	allergy to nettle; situations where fluid intake must be limited, such as severe heart or kidney disease
Children	use under 12 years not recommended, because of a lack of data
Pregnancy and breastfeeding	safety not established: use not recommended
Interactions	none reported
Adverse effects	mild digestive upset (nausea, vomiting, diarrhoea) and skin reactions (itching, rash, hives), frequency unknown
Overdose	no cases reported

In other words, the dangers of nettle are limited and well identified. They concern a few specific profiles, detailed below.

Leaf or root: two different uses

People talk about « nettle » for two parts of the plant, each with its own European monograph. The leaf tea, described above, has nothing to do with nettle root, used in men for the prostate.

Point	Nettle leaf	Nettle root
Traditional use recognised by the EMA	minor joint pain, urinary drainage	urinary complaints linked to benign prostatic hyperplasia, once serious causes have been ruled out by a doctor
As tea	2 to 4 g per cup, 3 to 6 times a day	2 g in 150 ml of water, 2 to 3 times a day
Duration	2 to 4 weeks	prolonged use possible
Who for	adults, not under 12 years	adult and elderly men
Adverse effects	mild digestive upset, skin reactions	nausea, heartburn, bloating, diarrhoea, allergic reactions
Signs that should make you see a doctor	symptoms that persist	fever, spasms, blood in the urine, pain when passing urine, urinary retention

The key point for the root: urinary problems in men must first be investigated by a doctor, who will rule out cancer or infection. Nettle root only comes afterwards, as an adjunct.

Nettle root and the prostate: what the main trial shows

The most often cited study is an Iranian trial published in 2005, double-blind and placebo-controlled, in 620 men with benign prostatic hyperplasia, followed for 6 months:

Measure	Nettle root	Placebo
Patients reporting an improvement in urinary symptoms	81%	16%
IPSS symptom score, out of 35	from 19.8 to 11.8	from 19.2 to 17.7
Maximum urine flow rate	+ 8.2 ml per second	+ 3.4 ml per second
PSA and testosterone	unchanged	unchanged

These results are striking, but they rest mainly on a single trial. The EMA only accepted nettle root as a traditional use, not as a use « well established » by studies. The fact that PSA does not change is also important: it remains a useful marker for medical follow-up, which nettle root does not distort.

Joint pain: what the studies are really worth

The EMA recognises nettle leaf for minor joint pain, but only as a traditional use. Its assessment report explains why it did not go further: the available studies are numerous, but not robust.

Study	What was done	Reported result
Open follow-up of 8,955 patients, 1997	dry nettle leaf extract in capsules, 2 times 2 capsules a day for 3 weeks, osteoarthritis or rheumatoid arthritis	64% of patients were able to clearly reduce their anti-inflammatory drug; pain at rest reduced by about 55%
Placebo-controlled crossover trial, 27 patients, 2000	fresh leaf applied for 30 seconds a day to the painful base of the thumb, for one week, versus a white dead-nettle leaf, which does not sting	pain and disability reduced more than with placebo after one week
Five studies covering 10,368 patients	extract equivalent to about 9.7 g of dried leaf a day, from 3 weeks to 12 months	no serious adverse effects; minor effects, mostly digestive or allergic, in 1.2 to 2.7% of patients

The EMA’s judgement is clear: the quality of these studies is « poor, not convincing ». The large follow-ups were open, with no placebo group, and most patients were already taking an anti-inflammatory drug. The 2000 trial was well controlled, but in only 27 people, and it looked at the sting of the fresh leaf on the skin, not at the tea.

These data are mainly of interest for safety: in more than 10,000 patients, at doses close to the monograph maximum, no serious effect was reported. They do not, however, allow us to promise that nettle tea will relieve your osteoarthritis. If your joints hurt, you need medical advice, and do not reduce a prescribed treatment on your own.

Nettle and blood sugar: a lead, not a treatment

Nettle is often presented as an « anti-diabetes » plant. A 2020 meta-analysis pooled the controlled trials carried out in people with type 2 diabetes:

Measure	Effect of nettle as a supplement
Trials included	8 trials, 401 participants
Fasting blood sugar	drop of about 18 mg/dL
Glycated haemoglobin, HbA1c	no significant drop
Insulin and insulin resistance	no significant change
Differences between studies	very large, which weakens the result

The EMA re-examined these trials during its 2022 review. Its conclusion: they do not justify changing the monograph. The authors themselves acknowledge short duration, small numbers and uncontrolled diets. In several trials, the product tested was not even precisely described, or did not match the preparations in the monograph. Some also used high doses, such as 10 g of dried leaves a day.

In practice, if you have diabetes and drink nettle in quantity, especially as an extract, tell your doctor: if the effect on blood sugar exists, it adds to that of your treatment. And HbA1c, the real marker of control, did not move in the meta-analysis. For the basics of diet, see our guide to type 2 diabetes: diet and prevention.

What nettle contains

100 g of blanched nettle leaves	Amount	Benchmark
Calories	42 kcal	–
Calcium	481 mg	60% of the reference value of 800 mg
Vitamin K	499 µg	more than six times the reference value of 75 µg
Fibre	6.9 g	–
Magnesium	57 mg	15% of 375 mg
Potassium	334 mg	–
Iron	1.6 mg	12% of 14 mg

These figures apply to cooked leaves, eaten as a soup or a purée. A herbal tea, made with 2 to 4 g of dried leaves, provides only a small part of these minerals, and almost no vitamin K, which does not dissolve in water. No reference database gives the composition of a nettle infusion.

A detail on potassium, often cited for the tea: an analysis cited by the EMA measured a potassium to sodium ratio of 448 to 1 in a decoction of leaves. The infusion therefore provides mostly potassium and almost no sodium, which is not a problem for a healthy person, but matters when a doctor is monitoring potassium, in kidney disease in particular.

The real dangers: for whom?

Kidneys, heart and dialysis

This is the EMA’s main contraindication: nettle makes you pass more urine, and it must not be used when a doctor has asked you to limit fluids, for example in heart failure or severe kidney failure, or on dialysis. Leaves eaten in quantity also provide potassium, which is monitored in these conditions.

Anticoagulants

Nettle leaves are among the vegetables richest in vitamin K: 499 µg per 100 g cooked. Vitamin K opposes the effect of vitamin K antagonist anticoagulants. With these drugs, the key is to keep your vitamin K intake steady from one day to the next: a large, unusual bowl of nettle soup can change the effect of the treatment. The tea probably contains very little, but in the absence of data, tell your doctor if you drink a lot of it. Newer anticoagulants, known as direct oral anticoagulants, do not depend on vitamin K.

Diuretics and other treatments

The EMA reports no interaction with medicines. As a precaution, if you already take a diuretic or a treatment whose balance depends on hydration, talk to your pharmacist before a course lasting several weeks: the effect on urine adds up.

Pregnancy and breastfeeding

The EMA advises against nettle tea during pregnancy and breastfeeding, because of a lack of safety data. This is not a demonstrated danger, but a precautionary principle. See our guide to eating during pregnancy.

Allergy

Nettle can cause skin reactions, itching and hives. If you have a known allergy to nettle, it is contraindicated.

Hay fever and hormonal effects: what we know

Nettle is also sold for seasonal allergies. The most recent controlled trial we found, published in 2017, gave 74 allergic people either a 150 mg nettle root extract tablet or a placebo for one month. Only 40 completed the trial. Symptoms improved in both groups, to a similar degree: the observed effect was therefore no better than placebo, and the authors call for larger and longer studies. This use does not appear in the EMA monographs.

Another rarely mentioned point: a case published in 2021 describes a 30-year-old woman who had milk discharge from the breast, unrelated to any pregnancy, after one month of a 500 mg nettle supplement taken for her allergies. Her tests were normal, and the problem disappeared a week after she stopped the supplement. A single case proves nothing, but it is a reminder of two things: concentrated supplements are not herbal teas, and you should always tell your doctor about them.

Form	Amount of plant	What to know
Leaf tea	2 to 4 g per cup	the monograph form, the best known
Dry extract in capsules	up to the equivalent of about 9.7 g of leaf a day in the studies	concentrated; used in the large joint follow-ups
Cooked leaves in soup	a 100 g portion	a vegetable: 499 µg of vitamin K, to know about if you take a vitamin K antagonist
Root supplement	depends on the product	another part of the plant, another use: the prostate

The traffic light by profile

Profile	Nettle tea
Healthy adult, 1 to 3 cups a day, for a few weeks	🟢 possible
Diuretic treatment	🟠 ask your pharmacist
Vitamin K antagonist anticoagulant	🟠 possible as tea, with caution; keep leaves in soup regular and mention them
Child under 12 years	🟠 not recommended by the EMA
Pregnancy, breastfeeding	🔴 not recommended by the EMA
Severe heart or kidney failure, dialysis, fluid restriction	🔴 contraindicated
Allergy to nettle	🔴 contraindicated

Side effects and the right dose

The adverse effects described by the EMA are mild: digestive upset and skin reactions. No overdose has been reported. The traditional dose is 2 to 4 g of dried leaves per cup; weigh them once so you can judge it by eye. In practice, one to three cups a day stay well below the monograph maximum of six cups. Do not go beyond a few weeks in a row without advice: the EMA sets a maximum duration of 2 to 4 weeks.

Can you drink it in the evening?

Yes, nettle contains no caffeine and does not stop you sleeping. But its effect on urine may wake you in the night to go to the toilet. If so, drink it in the morning and early afternoon instead. For sleep, see our guide to foods for sleep.

Eating nettles: precautions

• Do not eat them raw without preparation: the stinging hairs sting. Cooking, blanching for a few seconds in boiling water or drying neutralises them.
• Pick them away from roads and treated crops, and wash them carefully.
• Prefer young shoots, which are more tender.
• If you take a vitamin K antagonist, keep your intake steady, as with spinach or cabbage.

In soup, nettles are a vegetable rich in calcium and fibre. See our guides to foods high in calcium and vegetables high in fibre.

Real benefits and marketing claims

• « Rich in iron »: not really. 100 g of cooked leaves provide 1.6 mg of iron, 12% of the reference value, and it is non-haem iron, poorly absorbed. A herbal tea provides far less. For anaemia, see our guide to foods high in iron.
• « Draining, detox »: nettle increases urine volume, which is its recognised traditional use. But the liver and kidneys do not need a herbal tea to « detoxify » the body. See our guide to liver health and detox.
• Joint pain: traditional use recognised by the EMA for minor pain, based on long-standing use rather than robust clinical trials.
• Prostate: it is the root of nettle, not the leaf, that is used in this context. Do not confuse the two products.

For another common herbal tea, see thyme tea: dangers and contraindications.

Frequently asked questions

Is nettle tea dangerous?

Not for a healthy adult at one to three cups a day over a few weeks. It is contraindicated in severe heart or kidney disease with fluid restriction, and not recommended during pregnancy, breastfeeding and under 12 years.

How many cups of nettle tea a day?

The EMA states 2 to 4 g of leaves per cup, 3 to 6 times a day at most. One to three cups is a cautious benchmark, over 2 to 4 weeks.

Is nettle tea bad for the kidneys?

Not in a healthy person. It is contraindicated in severe kidney failure or on dialysis, when fluids must be limited.

Can you drink nettle tea if you take anticoagulants?

The EMA reports no interaction. The leaves are very rich in vitamin K: if you take a vitamin K antagonist, keep your intake steady and tell your doctor.

Can you drink nettle tea when pregnant?

The EMA does not recommend it during pregnancy or breastfeeding, because of a lack of safety data.

Does nettle tea help you lose weight?

No. It makes you pass more urine, which can lower the number on the scales a little through water loss, not fat.

Is nettle root effective for the prostate?

A 2005 trial in 620 men showed a clear improvement in urinary symptoms compared with placebo. The EMA recognises a traditional use, after medical advice to rule out a serious cause.

What is the difference between nettle leaf tea and root tea?

The leaves are used for minor joint pain and urinary drainage, for a few weeks; the root, in men, for urinary complaints linked to the prostate, with prolonged use possible.

Does nettle root change PSA?

No, according to the 2005 trial: PSA and testosterone remained unchanged.

Does nettle tea lower blood sugar?

A meta-analysis of 8 trials in people with type 2 diabetes found a drop in fasting blood sugar of about 18 mg/dL, with no significant effect on HbA1c. The EMA considers these trials too limited to conclude. If you are being treated, talk to your doctor.

Does nettle relieve hay fever?

This has not been shown. In a 2017 trial with a nettle root extract, symptoms improved just as much with placebo. The EMA does not recognise this use.

Does nettle treat osteoarthritis?

The EMA only recognises a traditional use for minor joint pain. The available studies, mostly open follow-ups without placebo, are judged to be of poor quality. They do, however, show good tolerance.

Do nettle supplements have side effects?

They are generally well tolerated: 1.2 to 2.7% of minor effects, digestive or allergic, in the large studies. A case of milk discharge from the breast, which disappeared on stopping, was published in 2021 with a 500 mg supplement.

Our sources

• EMA, Committee on Herbal Medicinal Products (HMPC), Community herbal monograph on Urtica dioica L., Urtica urens L., folium (EMA/HMPC/508015/2007).
• USDA FoodData Central, SR Legacy, « Stinging Nettles, blanched ».
• Regulation (EU) No 1169/2011, Annex XIII: reference values.
• EMA, HMPC. European Union herbal monograph on Urtica dioica L., Urtica urens L., radix, revision 1 (EMA/HMPC/322646/2023), 22 January 2025.
• Safarinejad MR. Urtica dioica for treatment of benign prostatic hyperplasia. J Herb Pharmacother, 2005 (PMID 16635963).
• EMA, HMPC. Assessment report on Urtica dioica L., Urtica urens L., folium (EMA/HMPC/508013/2007), and periodic review addendum (EMA/HMPC/489006/2020), 26 January 2022.
• Randall C et al. Randomized controlled trial of nettle sting for treatment of base-of-thumb pain. J R Soc Med, 2000 (PMID 10911825).
• Ziaei R et al. The effect of nettle (Urtica dioica) supplementation on the glycemic control of patients with type 2 diabetes mellitus: a systematic review and meta-analysis. Phytother Res, 2020 (PMID 31802554).
• Bakhshaee M et al. Efficacy of supportive therapy of allergic rhinitis by stinging nettle (Urtica dioica) root extract: a randomized, double-blind, placebo-controlled, clinical trial. Iran J Pharm Res, 2017 (PMID 29844782).
• Easton L et al. Stinging nettle (Urtica dioica): an unusual case of galactorrhea. Am J Case Rep, 2021 (PMID 34876549).