Nettle (Urtica dioica) has been used for centuries as medicine, food, fibre, dye, and even in textiles. The plant’s leaves and roots are the parts typically used in supplements, though they have different traditional applications. Nettle leaf is more commonly used for allergies and inflammatory conditions, while nettle root is the form usually studied for prostate health.

I should be upfront about what you’re getting into with nettle supplements: the research base is smaller than for many popular supplements, and much of the existing evidence comes from small trials. That said, there are a few areas where the data looks reasonably promising.

What is nettle?

Nettle belongs to the genus Urtica, which contains about 46 different species. The stems and leaves are covered with fine, hollow hairs called trichomes that act like tiny needles. When touched, these hairs inject a mixture of chemicals including histamine, acetylcholine, and formic acid into the skin, causing the familiar stinging sensation and temporary rash. This defence mechanism protects the plant from being eaten by animals and insects.

The name “nettle” comes from the Anglo-Saxon word “noedl,” meaning needle, while the Latin name “urtica” means burning. Both names reference that distinctive sting.

The most widely used species are stinging nettle (Urtica dioica) and small nettle (Urtica urens), which grow across Europe, Africa, Asia, and North America. Stinging nettle is the species used in most clinical research.

Despite its painful reputation when touched raw, nettle has a long history as a food plant. Young nettle leaves can be cooked (which neutralises the stinging chemicals) and eaten as a vegetable. The flavour is often compared to spinach, though a bit more earthy. In parts of Europe, nettle soup and nettle tea remain popular.

Nettle supplements come in several forms: dried leaf, dried root, liquid extracts, and freeze-dried capsules. The root and leaf preparations have somewhat different traditional uses and shouldn’t be considered interchangeable.

Potential benefits of nettle

1. Blood sugar control in type 2 diabetes

Type 2 diabetes involves chronically elevated blood sugar levels due to problems with insulin secretion or insulin resistance. Over time, poorly controlled blood sugar increases the risk of complications including kidney disease, nerve damage, retinopathy, and cardiovascular disease.

While insulin and oral hypoglycaemic medications remain the foundation of diabetes treatment, researchers have investigated whether plant-based supplements might offer additional benefit.

A systematic review and meta-analysis published in 2019 examined 8 randomised controlled trials involving 401 people with type 2 diabetes [1]. The studies used nettle preparations at daily doses ranging from 1.5 to 10 grams over 8 to 12 weeks. The pooled results showed that nettle supplementation significantly reduced fasting blood sugar concentrations compared with placebo.

However, there was no significant effect on insulin levels, the HOMA-IR index (a measure of insulin resistance), or glycosylated haemoglobin (HbA1c). That last point matters because HbA1c reflects average blood sugar control over 2-3 months and is generally considered more clinically meaningful than single fasting glucose measurements.

My honest take: the fasting glucose reduction is interesting but not compelling on its own. Without improvements in HbA1c, it’s hard to conclude that nettle provides meaningful long-term benefit for diabetes management. The sample sizes were also small. I wouldn’t take nettle expecting it to significantly improve diabetes control, though it’s probably safe enough as an addition to standard treatment for most people (with appropriate medical supervision given the drug interaction concerns discussed below).

2. Benign prostatic hyperplasia (enlarged prostate)

Benign prostatic hyperplasia (BPH) is extremely common in older men. About half of men over 50 have some degree of prostate enlargement, and this rises to roughly 80% by age 80. The enlarged prostate can squeeze the urethra and cause lower urinary tract symptoms including:

Difficulty starting urination
Weak urine stream
Feeling of incomplete bladder emptying
Frequent urination
Nocturia (waking at night to urinate)
Urge incontinence

Nettle root (not leaf) is the traditional preparation for prostate symptoms, and it’s one of the more commonly used herbal remedies for BPH in Europe.

A double-blind, placebo-controlled trial published in 2005 enrolled 620 patients with BPH and followed them for 6 months [2]. Those receiving nettle root extract showed improvements in the International Prostate Symptom Score (IPSS), maximum urine flow rate, and post-void residual urine volume compared with placebo.

A smaller randomised controlled trial from 2020 involving 60 patients with BPH found that 12 weeks of Urtica dioica root extract improved IPSS scores and also reduced markers of inflammation and oxidative stress (high-sensitivity C-reactive protein, malondialdehyde, and superoxide dismutase levels) [3].

The European Medicines Agency recognises nettle root as a “traditional herbal medicinal product” for relief of lower urinary tract symptoms related to BPH, though they note that the evidence comes from traditional use rather than large-scale clinical trials [4].

I’d characterise the evidence here as moderate. The 620-patient trial is a reasonable size, and the results were statistically significant. Nettle root appears to provide some symptomatic relief, though the effect size is modest. It’s not going to be as effective as prescription medications like alpha-blockers or 5-alpha reductase inhibitors, but for men with mild symptoms who prefer to try a natural approach first, it seems like a reasonable option to discuss with their doctor.

3. Knee osteoarthritis

Osteoarthritis is the most common form of arthritis, characterised by progressive cartilage breakdown, joint pain, and inflammation. The knee is one of the most frequently affected joints. Standard treatments include pain relievers, physical therapy, and in severe cases, joint replacement surgery.

Traditional medicine has long used nettle topically for joint pain. The practice is sometimes called “urtication”: fresh nettle leaves are deliberately applied to painful joints to induce a stinging reaction thought to have counter-irritant effects.

A randomised controlled pilot study from 2008 tested this approach in 42 people with knee osteoarthritis [5]. Participants applied fresh stinging nettle leaf to their painful knee daily for one week. The study found that nettle application reduced pain scores on the WOMAC osteoarthritis subscale compared with placebo (a non-stinging nettle species, Urtica galeopsifolia).

However, I should be clear about the limitations here. This was a very small study (42 participants) lasting only one week. The intervention also involved deliberately stinging yourself with nettles, which is rather different from taking a capsule. The approach is unconventional, and there’s not enough evidence to recommend it confidently.

Some research has also examined oral nettle extract for arthritis symptoms, though the evidence is even more limited. A study combining nettle with fish oil found some benefit, but you can’t separate nettle’s contribution from the fish oil [6].

For osteoarthritis, supplements with better evidence include glucosamine and chondroitin, curcumin, and boswellia.

Side effects of nettle

When taken orally as an extract or capsule, nettle is generally well tolerated. Reported side effects are usually mild and may include:

Digestive upset (diarrhoea, constipation, or stomach discomfort)
Allergic reactions (uncommon with processed supplements)

The more significant safety concern involves touching fresh nettle plants or their juice. Direct skin contact with the stinging hairs causes an immediate burning sensation, redness, and raised welts (urticaria) that typically resolve within 24 hours. In rare cases, more severe allergic reactions can occur.

People handling fresh nettles should wear gloves. The stinging chemicals are neutralised by cooking, drying, or processing, which is why nettle supplements and cooked nettle leaves don’t cause the same reaction.

Safety precautions (9 contraindications)

Pregnancy: Nettle may stimulate uterine contractions and should be avoided during pregnancy due to the risk of miscarriage. This is particularly important for nettle leaf preparations.
Breastfeeding: There’s insufficient safety data for nettle during lactation. It’s best avoided until more is known.
Lithium: Nettle has mild diuretic properties and may reduce how quickly the body eliminates lithium, potentially increasing lithium levels to toxic concentrations. Anyone taking lithium should avoid nettle or use it only under close medical supervision with lithium level monitoring.
Diabetes medications: Because nettle may lower blood sugar, combining it with insulin or oral hypoglycaemic drugs (glimepiride, metformin, glibenclamide, pioglitazone, and others) could theoretically increase the risk of hypoglycaemia. Diabetics should consult their doctor before taking nettle and monitor blood sugar closely if they do use it.
Blood pressure medications: Nettle may have mild blood pressure-lowering effects. When combined with antihypertensive drugs (ACE inhibitors, calcium channel blockers, diuretics, etc.), there’s a theoretical risk of blood pressure dropping too low. Discuss with your doctor if you take blood pressure medication.
Sedatives: High doses of nettle may cause drowsiness. Taking it with sedative medications or other central nervous system depressants could theoretically enhance sedation.
Warfarin and other anticoagulants: The aerial parts (leaves and stems) of nettle contain significant amounts of vitamin K, which promotes blood clotting and can interfere with warfarin’s anticoagulant effect. If you take warfarin, nettle leaf products could make your anticoagulation less effective and increase clotting risk. Nettle root contains less vitamin K and may be less problematic, but caution is still warranted.
Conditions affected by testosterone: Nettle may increase free testosterone levels by reducing binding to sex hormone-binding globulin (SHBG). This could theoretically worsen conditions characterised by androgen excess, such as polycystic ovary syndrome (PCOS) or hormone-sensitive cancers.
Before surgery: Given potential effects on blood sugar, blood pressure, and bleeding, it’s prudent to stop nettle supplements at least two weeks before scheduled surgery. Inform your surgical team about any supplements you take.

As with any supplement, discuss nettle with your healthcare provider before starting, particularly if you take any medications or have underlying health conditions.

The bottom line

Nettle has a long history of traditional use and some supporting clinical evidence, particularly for prostate symptoms. The evidence for blood sugar control shows modest effects on fasting glucose but no improvement in longer-term markers like HbA1c. For osteoarthritis, the research is too limited to draw conclusions.

If you’re considering nettle supplements, root preparations are the ones to choose for prostate health, while leaf preparations have been used more for other purposes. As with all supplements, quality varies between products, and nettle shouldn’t replace proven medical treatments for serious conditions.

References

Ziaei R, Foshati S, Hadi A, 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;34(2):282-294. PubMed
Safarinejad MR. Urtica dioica for treatment of benign prostatic hyperplasia: a prospective, randomized, double-blind, placebo-controlled, crossover study. J Herb Pharmacother. 2005;5(4):1-11. PubMed
Jalili C, Salahshoor MR, Hoseini M, et al. Therapeutic effect of Urtica dioica on clinical and biochemical parameters in patients with benign prostatic hyperplasia: A randomized controlled trial. Afr J Urol. 2020;26:70. PubMed
European Medicines Agency. Urtica dioica L., Urtica urens L., radix. Herbal medicines for human use assessment. EMA
Randall C, Meethan K, Randall H, Dobbs F. Nettle sting of Urtica dioica for joint pain—an exploratory study of this complementary therapy. Complement Ther Med. 2008;16(2):66-72. PubMed
NHS. Complementary and alternative medicine. NHS