Stinging Nettle Root: Testosterone, Prostate and More

Summary: Stinging nettle root is often sold as a way to raise “free” testosterone, but that idea comes from test-tube studies, and a newer lab study found its best-known compound binds only weakly to the protein that carries testosterone in the blood. No trial has shown it raises testosterone in people. Its more realistic uses are modest relief of urinary symptoms from an enlarged prostate a small drop in blood sugar in people with type 2 diabetes, mostly from nettle leaf studies.

Stinging nettle root turns up in “testosterone boosters” and men’s prostate formulas. Supplement labels often claim it frees up testosterone so your body can use more of it. So what does stinging nettle root actually do, and how good is the evidence? Here’s what the research says, in plain English.

What is stinging nettle root?

Stinging nettle (Urtica dioica) is a common wild plant with tiny stinging hairs on its leaves and stems. The leaves are eaten cooked or made into tea, while extracts of the root are used mainly for urinary problems in older men.

In the European Union, nettle root is registered as a “traditional herbal medicinal product” for relieving lower urinary tract symptoms linked to benign prostatic hyperplasia, but only after a doctor has ruled out serious conditions [1]. “Traditional” means the registration is based on long-standing use, not on proof from clinical trials.

The root contains lignans, plant compounds with a structure that lets some of them latch onto hormone-carrying proteins. One of them, (−)-3,4-divanillyltetrahydrofuran, has drawn the most attention because of how strongly it bound to a hormone-carrying protein in early lab tests [2].

How stinging nettle root is supposed to affect testosterone

In the blood, testosterone is partly carried by a protein called sex hormone-binding globulin (SHBG). SHBG also carries dihydrotestosterone (DHT, a stronger hormone made from testosterone) and estradiol (the main form of estrogen). SHBG sets the balance between bound and “free” hormone and controls how much reaches your tissues [3].

The theory behind nettle supplements is simple: if a nettle compound takes up the spot on SHBG where testosterone normally sits, more testosterone is left free.

• In German lab tests in the 1990s, all but one of the nettle root lignans tested bound to human SHBG in a test tube, and the binding of 3,4-divanillyltetrahydrofuran was described as “outstandingly high” [2].
• A follow-up study found it had the strongest binding of all the lignans tested and pushed DHT off SHBG in a test tube [4].
• A more detailed study published in 2020, which mapped the compound inside SHBG at the atomic level, found it binds SHBG with “relatively low affinity” (it holds on only loosely) compared with testosterone and estradiol. In the presence of zinc, its binding was “almost completely lost.” It did free up testosterone in a cell culture experiment [3].

So the idea works in a dish, but the compound appears to be a weak competitor for SHBG, and none of this shows what happens after you swallow a capsule. A detailed review of nettle root concluded that its mechanism is still unclear and that it isn’t known whether lab or animal results predict effects in people [5].

Does stinging nettle root raise testosterone in people?

We couldn’t find any human trial that tested stinging nettle root, or 3,4-divanillyltetrahydrofuran on its own, with testosterone as the main outcome. The closest evidence points the other way: in a six-month placebo-controlled prostate trial of 620 men, blood testosterone levels didn’t change with nettle root [6]. (There are reasons to be cautious about that trial, explained in the prostate section below.)

A 2011 case report is sometimes linked to nettle. A 19-year-old man saw his doctor about fluid retention, low sex drive and erection problems and was found to have high testosterone along with high luteinizing hormone (LH, the pituitary hormone that signals the testes to make testosterone). He had been taking a supplement called ActivaTe Xtreme, bought online, and the doctors said its ingredients raise testosterone by several different mechanisms [7]. But the published report doesn’t list nettle among the ingredients or say which ingredient was responsible, so it can’t tell us anything about nettle itself.

Products sold as purified 3,4-divanillyltetrahydrofuran are another question mark. We couldn’t find any independent published testing of what these products actually contain.

If testosterone is what you’re interested in, our reviews of ashwagandha and D-aspartic acid look at herbs and supplements that have at least been tested in human trials.

Stinging nettle root for an enlarged prostate

Benign prostatic hyperplasia (BPH) is a non-cancerous enlargement of the prostate that’s common as men get older. It can cause a weak urine stream, needing to go often (including at night), and trouble emptying the bladder. Trials usually measure it with the International Prostate Symptom Score (IPSS), a 0–35 questionnaire where lower is better.

This is where stinging nettle root has the most human research, but the results are mixed:

• An early systematic review (a careful pooling of the trials on a question) found “no convincing evidence” that nettle root on its own helps BPH, though it said nettle might work when combined with other plant extracts [8].
• A German one-year trial gave 246 men 459 mg of dry nettle root extract a day or a placebo (dummy pill). Symptom scores fell from 18.7 to 13.0 with nettle and from 18.5 to 13.8 with placebo. That difference was statistically significant but only about one point on the 35-point scale, and urine flow and the amount of urine left in the bladder improved about equally in both groups [9].
• The largest nettle-only trial, from Iran, reported much bigger effects in 620 men over six months: 81% felt their symptoms improved with nettle versus 16% with placebo, and symptom scores fell from 19.8 to 11.8 versus 19.2 to 17.7 [6]. However, dozens of the trial author’s other papers have since been retracted or flagged by journals over concerns about the validity of the data; one example is [10]. This trial itself hasn’t been retracted, but its results are far larger than in other trials, so they should be treated with caution.

Nettle root is more often studied in combination with saw palmetto. In a trial of 257 men, a capsule with 160 mg saw palmetto extract and 120 mg nettle root extract, taken twice a day for 24 weeks, lowered symptom scores by about 6 points versus 4 points with placebo [11]. In a 48-week trial of 543 men, the same combination improved symptoms about as much as finasteride, a prescription prostate drug, with fewer side effects, but there was no placebo group [12]. These combination trials can’t tell you how much of the effect comes from the nettle.

Overall, a detailed review concluded that a few randomized trials suggest a benefit for one nettle root extract, but “the significance and magnitude of the effect remains to be established” [5]. For another plant compound used for the prostate, see our review of beta-sitosterol.

If you have urinary symptoms, see a doctor before trying any supplement. The European regulator’s guidance also says to see a doctor if symptoms get worse, or if you get fever, spasms, blood in your urine, pain when urinating, or can’t pass urine [1].

Stinging nettle and blood sugar

The main blood sugar trial used nettle leaf extract, not stinging nettle root [13], and the reviews below pooled nettle products in general, so these results don’t automatically apply to root supplements.

• In a placebo-controlled trial, 92 people with advanced type 2 diabetes (46 per group) took a 500 mg nettle leaf extract capsule every eight hours for three months alongside their usual diabetes medicines. Fasting blood sugar, blood sugar two hours after eating, and HbA1c (a measure of average blood sugar over about three months) all improved compared with placebo [13].
• A 2020 meta-analysis (a study that pools results from many trials) of 8 trials with 401 people found nettle lowered fasting blood sugar by about 18 mg/dL (about 1 mmol/L). It found no significant change in insulin, insulin resistance or HbA1c, and the results varied a lot between studies [14].
• A 2022 meta-analysis of 13 trials found a similar drop in fasting blood sugar (about 17 mg/dL) and also reported lower HbA1c, triglycerides and systolic (top-number) blood pressure, but no change in cholesterol or body mass index (BMI) [15].

These are small, short trials with very mixed results, and the two reviews disagree on HbA1c. Nettle isn’t a substitute for diabetes treatment. If you take diabetes medicines, talk to your doctor first, because adding anything that lowers blood sugar could make it drop too low.

Other uses of stinging nettle

• Hay fever: In a small trial, 98 people with allergic rhinitis took a freeze-dried nettle preparation or a placebo for one week, and 69 finished (the study abstract doesn’t say which part of the plant was used). Nettle was rated a little better overall, but only slightly better in daily symptom diaries [16]. Memorial Sloan Kettering Cancer Center (MSKCC) says evidence is lacking for allergies [17].
• Joint pain: MSKCC notes that clinical trials support applying nettle to the skin for arthritis, but larger studies are needed [17].

How much stinging nettle root is used?

Doses depend on the type of extract. For prostate symptoms, the EU herbal monograph lists, for example, 150–160 mg of one dry root extract three times a day (450–480 mg a day), or 460 mg once a day. For tea, it lists 2 grams of the dried, cut root steeped in 150 mL of water, two to three times a day. It says long-term use is possible and that nettle root isn’t for people under 18 [1].

There’s no established dose of stinging nettle root for testosterone, because there’s no evidence it works for that.

Stinging nettle root side effects and safety

Nettle root is generally well tolerated, and a detailed review rated the risk of side effects as very low [5]. Things to know:

• Common side effects: The EU monograph lists stomach and gut complaints (nausea, heartburn, a feeling of fullness, gas, diarrhea) and allergic reactions (itching, rash, hives). How often these happen isn’t known [1].
• Hormone-related reports: MSKCC lists case reports of breast enlargement in a man and nipple discharge in a woman linked to nettle tea [17]. In another case, a 30-year-old woman taking 500 mg of nettle for allergies developed nipple discharge, which cleared up a week after she stopped (she was also using a hormonal contraceptive implant) [18].
• Blood sugar and medicines: MSKCC reports a case of low blood sugar in a 78-year-old man taking an herbal remedy containing nettle for BPH. Animal studies suggest nettle could add to the effects of diuretics (water pills) and blood pressure medicines and could interact with drugs processed by certain liver enzymes, though how much this matters in people isn’t known [17].
• Missing safety tests: According to the EU monograph, adequate tests for genetic damage, effects on reproduction and cancer risk haven’t been done [1]. There’s no safety information for pregnancy or breastfeeding, so if that applies to you, ask your doctor first.

If you take any medicines or have a health condition, check with your doctor or pharmacist before using nettle supplements.

The bottom line on stinging nettle root

Stinging nettle root doesn’t have good evidence as a testosterone booster. The SHBG idea comes from test-tube studies, newer lab work suggests its key compound binds SHBG only weakly, and the only trial we found that measured testosterone in men (from an author whose other work has faced data concerns) reported no change. For prostate symptoms, nettle root may help a little, especially combined with saw palmetto, but the trials are mixed and the most positive one is hard to trust. Nettle, mostly studied as leaf extract, may lower blood sugar slightly in people with type 2 diabetes. If you have urinary symptoms or diabetes, see your doctor rather than treating yourself.

This article is for general information only and isn’t medical advice. Talk to your doctor or another qualified health professional before starting a new supplement. See our medical disclaimer.

References

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2. Schöttner M, Gansser D, Spiteller G. Lignans from the roots of Urtica dioica and their metabolites bind to human sex hormone binding globulin (SHBG). Planta Med. 1997;63(6):529-532. doi:10.1055/s-2006-957756
3. Round P, Das S, Wu TS, Wähälä K, Van Petegem F, Hammond GL. Molecular interactions between sex hormone-binding globulin and nonsteroidal ligands that enhance androgen activity. J Biol Chem. 2020;295(5):1202-1211. doi:10.1074/jbc.RA119.011051
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