Ashwagandha Side Effects: For Women, Men and Who Should Avoid It (UK)

Common ashwagandha side effects

Ashwagandha (Withania somnifera) is an evergreen shrub from India, the Middle East and parts of Africa. Its root has been used in Ayurvedic practice for centuries, and it is now one of the UK’s most popular supplements for stress. In studies, side effects are usually mild and similar to a placebo. The ones people report most are:

• Drowsiness or feeling sluggish, especially when taken in the morning
• An upset stomach, nausea or loose stools, more likely on an empty stomach
• Headaches
• Vivid dreams for some people (see vivid dreams)

These usually settle if you lower the dose, take it with food or move it to the evening. Read our guide on when to take ashwagandha.

Less common and rare side effects

Liver injury (rare): warning signs and when to see a GP

A small number of liver injury cases linked to ashwagandha supplements have been published, including case series from Iceland, the US and India. It is rare and can’t be predicted. In the published cases it appeared 2 to 12 weeks after starting, and most people recovered over a few months after stopping. The worst outcomes were in people who already had liver disease.

iStop taking it and ask for an urgent GP appointment, or call NHS 111, if you notice:

• yellow skin or yellowing of the whites of your eyes
• dark pee or pale poo
• itchy skin with no obvious cause
• pain or discomfort under your right ribs, nausea or unusual tiredness

Tell the doctor every supplement you take, including CBD oils with added herbs. More detail: ashwagandha and the liver in the UK safety review.

Ashwagandha and your thyroid (hypothyroidism)

Ashwagandha can raise thyroid hormone levels in some people, and there are case reports of an overactive thyroid. This matters most if you already have a thyroid condition or take thyroid medicine.

In a small 2018 trial in 50 adults with subclinical hypothyroidism, eight weeks of 600mg ashwagandha root extract a day shifted TSH, T3 and T4 levels compared with placebo. Case reports also describe thyrotoxicosis (too much thyroid hormone), including a 73-year-old woman who used ashwagandha for two years to self-treat an underactive thyroid and developed a fast heart rhythm, which settled after she stopped.

If you have hypothyroidism or any thyroid condition, or take levothyroxine, speak to your GP before taking ashwagandha. Don’t use it in place of thyroid medicine. Signs of too much thyroid hormone include a racing heartbeat, trembling, sweating and weight loss despite a bigger appetite. Weight gain and irregular or heavy periods can be signs of an underactive thyroid itself, so get new symptoms checked.

Does ashwagandha cause weight gain?

Weight gain is not a side effect that clinical trials report. A 2026 review of 23 trials in healthy adults found side effects were mild and infrequent, mainly stomach discomfort, headaches and drowsiness, and also turned up in placebo groups. In the one small trial that tracked weight, 52 stressed adults took ashwagandha or a placebo for eight weeks, and the ashwagandha group did not put on weight.

iSome people still notice appetite changes, and weight naturally drifts. Unexplained weight loss matters more, as it can be a sign of an overactive thyroid (see ashwagandha and your thyroid). If a change worries you, stop taking it and speak to your GP.

Mental side effects

Most people take it to feel calmer, but a few report feeling flat, restless or more anxious. If your mood changes for the worse, stop taking it.

• Sleepiness: the most common one, which is why many people take it in the evening.
• Feeling flat: see does ashwagandha make you feel emotionally numb?
• Restlessness, anxiety or low mood: rare. Speak to your GP if low mood carries on after stopping.

iIf you take antidepressants, sleeping tablets or any other medicine for your mental health, check with your GP or pharmacist first. Ashwagandha may add to the effect of sedatives, and it is not a replacement for prescribed treatment.

Can you take ashwagandha long term?

Nobody knows yet. The US National Center for Complementary and Integrative Health (NCCIH) says ashwagandha may be safe in the short term, up to 3 months, but there isn’t enough information on long-term safety.

• Trials: a 2026 review of 23 trials (2,317 healthy adults, up to 180 days) found liver, kidney and hormone markers stayed normal, but had little data beyond 6 months.
• One year: a 12-month study of 191 adults reported only mild side effects, but had no placebo group and was too small to catch rare liver reactions.
• Cycling: no trial shows breaks are needed, but reviewing it after 8 to 12 weeks and pausing for a few weeks is a cautious habit.
• The UK view: the Committee on Toxicity hasn’t published one yet; see the UK section below.

Stopping: ashwagandha isn’t known to be addictive. One 2025 case report described a racing heart, poor sleep and anxiety after a young man suddenly stopped 600mg a day, though his anxiety may simply have returned. After months of use, cutting down gradually is a sensible precaution. See also how long ashwagandha takes to work.

Does ashwagandha cause hair loss?

There’s no good evidence that it does: trials haven’t reported it, and we found no study linking the two. Two indirect links are worth knowing:

• Thyroid: ashwagandha can change thyroid hormone levels, and the NHS lists hair loss as a symptom of both an overactive and an underactive thyroid. If it comes with a racing heart, weight changes or tiredness, see your GP.
• Testosterone: small trials in men found modest rises, within the normal range. No study has shown this causes male pattern hair loss, which usually runs in families.

Timing can mislead too. Shedding often starts around 3 months after illness, surgery, big weight loss, stress or a new medicine (telogen effluvium), and usually settles on its own. See why is my hair falling out? and stress and hair loss.

Ashwagandha side effects for women

• Pregnancy: avoid ashwagandha. There are long-standing concerns that high doses could increase the risk of miscarriage.
• Breastfeeding: avoid it. There is no good research on whether it passes into breast milk. Read our guide to ashwagandha and breastfeeding.
• Trying to conceive: speak to your GP first, as ashwagandha may affect reproductive hormones.
• Thyroid conditions: women are more likely to have thyroid problems, so check before taking it. See ashwagandha and your thyroid.
• PCOS and hormone-sensitive conditions: ask your doctor first. Our guide to ashwagandha for PCOS looks at the research.

Ashwagandha and periods

There is very little research on ashwagandha and periods. Trials in women have mostly looked at stress, sleep, sexual function and perimenopause, and we haven’t found one that reports period changes as a side effect, though none was designed to look for them. Some women report cycle changes online, which are hard to separate from stress itself, as stress and big weight changes can both make periods irregular.

If your periods change after starting it, stop and see whether they settle, and see your GP if they stay irregular or you bleed between periods. Avoid it in pregnancy and while breastfeeding, and speak to your GP first if you are trying to conceive. For cycles, PCOS and menopause, read ashwagandha for women.

How much ashwagandha per day for females? The same range as for men, mostly 300mg of root extract twice a day in trials. See how much ashwagandha per day.

If you want calm and better sleep without ashwagandha, magnesium is a gentler place to start. See magnesium glycinate and ashwagandha vs magnesium.

Ashwagandha side effects for men

Many men take ashwagandha for stress, sleep, training recovery or testosterone. A 2021 systematic review concluded that ashwagandha root and root and leaf extracts had positive effects on testosterone levels in men, although the studies were small.

iThe side effects for men are the same as for anyone: drowsiness, stomach upset and, rarely, liver or thyroid effects. Because it can affect hormones, ask your doctor first if you have a hormone-sensitive condition such as prostate cancer, or are having fertility treatment.

For the testosterone, sperm and strength trials, see ashwagandha for men, and for how stress shows up in men, our Movember guide to stress in men.

Does ashwagandha make you feel emotionally numb?

“Does ashwagandha kill emotions” has become one of the fastest-rising ashwagandha searches in the UK. Some people, mostly in online forums, describe feeling flat, detached or emotionally numb while taking it.

Here is what we know honestly:

• Emotional blunting has not been reported as a side effect in clinical trials, which mostly looked at stress, sleep and anxiety scores.
• There is no proven mechanism. One plausible explanation is that by taking the edge off stress, some people feel less of everything, which can feel like numbness.
• People react differently to supplements, so personal reports still matter.

iWhat to do: if you feel flat, low or detached, stop taking it and see whether you feel like yourself again within a week or two. If low mood carries on, talk to your GP.

Who should avoid ashwagandha?

• people who are pregnant, breastfeeding or trying to conceive
• anyone with a thyroid condition
• anyone with liver disease
• people with autoimmune conditions
• anyone due to have surgery (stop at least two weeks before)
• children and teenagers under 18
• people taking any of the medicines listed below

Medicine and supplement interactions

Ashwagandha may interact with:

• Thyroid medicine, such as levothyroxine
• Diabetes medicines, as it may lower blood sugar
• Blood pressure medicines, as it may lower blood pressure
• Sedatives and sleeping tablets, including benzodiazepines
• Immunosuppressants
• Anti-seizure medicines

iBe careful stacking it with other sedating supplements, such as high doses of valerian or melatonin. If you take any regular medication, speak to your pharmacist before starting ashwagandha.

Is ashwagandha a drug?

Not in the UK. It is sold as a food supplement, regulated as food rather than as a licensed medicine, and it isn’t a controlled drug. It is a traditional Ayurvedic medicine in India, though, and it can still act on your body like one, which is why it interacts with the medicines above.

Is ashwagandha safe and legal in the UK?

Ashwagandha is currently legal to sell as a food supplement in the UK. In 2024 the Food Standards Agency asked for evidence on its safety, citing concerns about the thyroid, blood sugar and the liver, and the UK’s Committee on Toxicity (COT) is reviewing it. The COT discussed a third draft statement on 8 September 2026, kept private because it contains unpublished information. No decision has been published yet.

The FSA hasn’t published formal consumer advice either, but while the review continues it told Which? in June 2026 that it would advise people with pre-existing liver conditions and pregnant women to avoid ashwagandha supplements.

Elsewhere in Europe, Denmark banned ashwagandha in food supplements in 2023, saying a safe intake could not be established, and the Netherlands advises people not to use it, though it hasn’t banned it. Denmark’s decision has been criticised by some researchers, and most countries still allow it.

We follow the FSA’s review closely and will update this page when it reports. Our guide to ashwagandha in the UK covers the regulation in more detail.

How to use ashwagandha more safely

1. Start low. Begin with the lowest suggested dose on the label.
2. Be consistent, not aggressive. More is not better.
3. Avoid stacking sedatives. Don’t combine it with several other sleep aids at once.
4. Take breaks. Many people take it for up to eight to twelve weeks, then pause.
5. Choose a tested product from a brand that publishes lab reports.
6. Stop if something feels wrong, and see a doctor for any signs of liver problems.

If you take Flow, and ashwagandha-free options

If you take Flow CBD Oil

Our Flow CBD Oil combines broad spectrum CBD with ashwagandha extract and maca in MCT oil, so everything on this page applies to it. Don’t take it if you are under 18 or have a liver, thyroid or autoimmune condition, check with your pharmacist first if you take regular medication, and don’t add a second ashwagandha supplement. We don’t recommend our products during pregnancy or breastfeeding.

How much ashwagandha is in it? The Flow product page doesn’t currently state the amount of ashwagandha per drop, so we can’t compare it with trial doses here; ask us if your GP needs it. Servings are set by the CBD: about 4 drops of the 500mg or 2 drops of the 1,000mg give 10mg. More in CBD and ashwagandha.

The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.

An ashwagandha-free evening option

If ashwagandha isn’t right for you, our Magnesium Glycinate Sleep Complex has no ashwagandha and no CBD. It’s a berry drink powder with 290mg of magnesium a serving from bisglycinate and citrate, plus glycine, L-theanine and herbal extracts. Magnesium contributes to a reduction of tiredness and fatigue. It isn’t a like-for-like swap (see ashwagandha vs magnesium).

Magnesium Glycinate Sleep Complex

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Value: the 1,000mg Flow costs less per mg of CBD than the 500mg. Subscribe and Save lowers the price of every order, and you can skip, pause or cancel any time.

• Our CBD products, Flow included: every batch tested at ISO 17025 labs (reports on request via our lab testing page), broad spectrum and THC free, and on the FSA public list, linked to validated applications.
• All our products: made in the UK, vegan and alcohol-free.
• Tracked Royal Mail delivery, dispatched the same day if you order before 3pm Monday to Thursday (delivery details).
• Unopened, unused items can be returned within 14 days, once approved (returns policy).

They’re food supplements, not medicines. Choosing? Flow if you want ashwagandha in a daytime routine and none of the cautions apply to you; the Magnesium Complex or our Reishi Cacao (a reishi hot chocolate that contains a little natural caffeine) if you’d rather avoid it.

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