Best Sleep Supplements in the UK: What Actually Has research

What it claims

Sleep supplements promise faster sleep, deeper sleep and waking refreshed, without the grogginess of sleeping pills. The most popular ingredients are magnesium, glycine, L-theanine, apigenin (from chamomile), ashwagandha and tart cherry. Many products also hint at melatonin effects.

What the evidence shows

CBT-I comes first

For ongoing insomnia, the NHS says a GP may offer cognitive behavioural therapy for insomnia (CBT-I), either face to face or through an online programme. It changes the habits and thoughts that keep you awake and has the strongest evidence of any option. GPs now rarely prescribe sleeping pills.

Melatonin is not a supplement in the UK

Melatonin is prescription only in the UK, mainly for short-term use in people aged 55 and over or under specialist care. That is why we do not recommend any melatonin product. Imported gummies are not checked for dose or quality.

Magnesium

A 2021 review of three small trials in older adults found people fell asleep about 17 minutes faster, but the evidence quality was low to very low. A 2026 review of 12 trials found the results inconsistent and said magnesium should not be a routine insomnia treatment. It is most likely to help if your diet is low in magnesium. The NHS says 400mg or less a day from supplements is unlikely to cause harm.

L-theanine

An amino acid found in tea. A 2025 meta-analysis of 18 trials found small improvements in how quickly people felt they fell asleep, daytime tiredness and overall sleep quality. The effects were small and self-reported, and many trials mixed it with other ingredients.

Glycine

Small Japanese trials found 3g before bed improved how rested people felt, possibly by lowering core body temperature (review). The trials were short and mostly from one research group with industry links.

Tart cherry

Montmorency cherries contain a little natural melatonin. A small 2012 trial of 20 people found longer total sleep time with concentrate twice a day for a week. Promising but tiny.

Chamomile and apigenin

A 2024 meta-analysis found chamomile improved sleep quality scores and night waking, but not total sleep time. Apigenin capsules on their own have very little human sleep research; a cup of chamomile tea is the low-cost way to try it.

Ashwagandha

Some trials suggest better sleep, but the UK FSA asked its Committee on Toxicity to assess ashwagandha after reports of possible liver and thyroid effects, and Denmark banned it in supplements in 2023. The ban is disputed by some researchers (editorial), but until UK advice is clearer we do not recommend it.

Who might reasonably try it

• Adults with occasional poor sleep who have already tried basic sleep habits.
• People whose main problem is a busy mind at bedtime (L-theanine) or who eat little magnesium-rich food (magnesium).

Who should be careful

• Pregnant or breastfeeding women: check with your midwife or GP before any sleep supplement.
• People on regular medicine: especially for blood pressure, mood, epilepsy or other sleep medicines. Ask a pharmacist.
• Kidney disease: avoid magnesium supplements unless your doctor agrees.
• Snoring, gasping or very sleepy days: see a GP, as this may be sleep apnoea, which supplements will not fix.
• Insomnia lasting months: see a GP about CBT-I.

If you want to try it: what to look for

• One ingredient at a time at a dose used in trials: 200mg L-theanine, 3g glycine, magnesium up to 400mg a day.
• Third-party testing such as Informed Sport where available.
• No melatonin or ashwagandha in the ingredients list.
• A two to four week trial with a sleep diary, then stop if there is no change.

Simple sleep habits that work alongside any supplement

Before spending money, the NHS suggests some basics that help most people: keep regular sleep and wake times, including at weekends; keep the bedroom dark, quiet and cool; avoid caffeine after lunchtime; limit alcohol, which fragments sleep later in the night; and get daylight in the morning. If you lie awake for a long time, getting up and doing something calm in dim light until you feel sleepy is a core part of CBT-I.

How to tell if a supplement is helping

Sleep is very open to the placebo effect, so it helps to measure. For two weeks before starting, note roughly what time you went to bed, how long it took to fall asleep, how many times you woke and how rested you felt (score out of 10). Keep the same notes for the first four weeks on the supplement. If your scores have not clearly improved, stop and save your money. Wearable sleep scores can be a rough guide, but they are not diagnostic and can misjudge sleep stages, so trust how you feel during the day too.

Our picks at a glance

How we chose

We picked single-ingredient products at trial doses from UK brands with live UK prices. We favoured third-party tested products where they exist. We excluded melatonin (prescription only), ashwagandha (under UK safety review) and multi-ingredient blends with low hidden doses.

Viridian High Potency Magnesium Bisglycinate

An unbuffered glycinate giving 200mg of magnesium in two capsules, well inside the NHS guide. Caveat: no published third-party test, and the sleep evidence is mixed.

Puresport Ultra Magnesium

Informed Sport certified, so each batch is tested by an independent lab. Caveat: it also contains vitamin D3 and beetroot, and costs more than a plain glycinate.

Nature's Best L-Theanine 200mg

A low-cost 200mg capsule, the dose in many trials. Caveat: effects in trials were small and self-reported, and there is no published third-party test.

Bulk Glycine Powder

The cheapest way to try the 3g bedtime dose. Caveat: the human research is small and short, and there is no published third-party test.

CherryActive Concentrate 946ml

The tart cherry concentrate used in a small UK sleep trial; the sachet format is Informed Sport certified. Caveat: tiny evidence base, and each serving contains natural fruit sugar.

Bottom line

Supplements are at best a small nudge for sleep. If you want to try one, choose a single ingredient at a trial dose, give it a few weeks and keep a diary. For insomnia that lasts, ask your GP about CBT-I, which has far stronger evidence than anything in a tub.