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The short answer No sleep supplement has strong evidence behind it. Melatonin has the most research, and it helps body-clock problems like jet lag more than everyday insomnia. Magnesium, ashwagandha, L-theanine and lavender have small, promising trials. Valerian, chamomile tea, tart cherry and CBD have little or mixed support, and kava carries a liver-injury warning. For insomnia that keeps coming back, CBT-I beats every bottle.
The table grades each option by how much good research exists, not by how many people swear by it. A low grade doesn’t mean a supplement can’t help you. It means nobody has shown it reliably helps people in general.
| Supplement | Evidence | What the research found | Main cautions |
|---|---|---|---|
| Melatonin | Moderate evidence | About 7 minutes faster to fall asleep across 19 trials; more useful for jet lag and body-clock problems. AASM suggests against it for chronic insomnia. | Labels often inaccurate; keep away from children |
| Magnesium | Limited evidence | Three small trials in older adults: about 17 minutes faster to fall asleep, low-quality evidence | Diarrhea; kidney disease; several drug interactions |
| Ashwagandha | Limited evidence | Five trials, 400 people: small but real improvement in overall sleep, larger in people with insomnia | Rare liver injury; avoid in pregnancy and thyroid disease |
| L-theanine | Limited evidence | 18 pooled trials: small gains in self-rated sleep quality and daytime functioning, many using blends | Few studies of L-theanine alone |
| Lavender (scent) | Limited evidence | Inhaled lavender oil improved self-rated sleep quality across 11 small trials | Study quality low; not for swallowing |
| Glycine | Weak evidence | Small Japanese trials; in one, sleep-restricted volunteers reported less next-day fatigue | Very little independent research |
| Valerian | Weak evidence | Effects below the threshold that matters clinically; AASM suggests against it | Long-term safety unknown |
| Chamomile | Weak evidence | Some better sleep-quality scores; the one insomnia trial found no change | Allergy if you react to ragweed |
| Tart cherry | Weak evidence | Tiny early studies were positive; two recent trials found no effect | Sugar and calories in juice form |
| Tryptophan and 5-HTP | Weak evidence | AASM suggests against tryptophan for insomnia | Serotonin toxicity with some antidepressants |
| CBD | Weak evidence | NCCIH: insufficient evidence for any sleep disorder | Liver injury, drug interactions; not a legal supplement per FDA |
| Kava | Weak evidence | Very little sleep research | Linked to serious, sometimes fatal liver injury; avoid |
Two over-the-counter drugs, diphenhydramine and doxylamine, often sit on the same shelf. They’re antihistamines, not supplements, and we cover them separately below.
How we graded these
Strong would mean consistent results from several good-sized, well-run trials. Nothing here qualifies. Moderate means a meta-analysis or several decent trials agree on a real, if modest, effect. Limited means a few small trials point the same way, often with weak methods or industry funding. Weak means little research, mixed results, null results, or a guideline that recommends against it.
The big guideline here is the American Academy of Sleep Medicine’s 2017 review of drugs for chronic insomnia. It made weak recommendations against melatonin, valerian, tryptophan and diphenhydramine. Under its grading system, a weak recommendation isn’t proof that something fails. It means the panel couldn’t find clinically meaningful benefits in the trials it reviewed.
Melatonin
Moderate evidenceMelatonin is a hormone your brain releases in the evening, and the supplement is best at nudging the timing of sleep. A 2013 meta-analysis of 19 trials with 1,683 people found it helped people fall asleep about 7 minutes sooner and sleep a bit longer, effects the authors called modest. For jet lag, NCCIH reports that small studies suggest it may reduce symptoms after both eastward and westward flights.
The AASM recommendation against it for chronic insomnia was based on trials of 2 mg prolonged-release melatonin in adults over 55, where the effect on sleep quality wasn’t clinically significant. Quality control is a real problem too: a 2023 analysis found 22 of 25 melatonin gummy products were inaccurately labeled, and NCCIH cites a CDC estimate of 11,000 emergency visits for children 5 and under who got into melatonin unsupervised. Our melatonin dosage guide covers the doses studied and timing.
Magnesium
Limited evidenceA 2021 meta-analysis pooled three small trials in 151 older adults and found magnesium helped them fall asleep about 17 minutes faster than placebo, but rated the evidence low to very low quality. NCCIH says there is very little research on magnesium for insomnia, and it notes the 350 mg daily upper limit for supplements in adults. High intakes cause diarrhea, nausea and cramps. The details, including which forms are gentler on the stomach, are in magnesium for sleep and glycinate vs citrate.
Ashwagandha
Limited evidenceThis herb has a better trial record than most. A 2021 meta-analysis of five randomized trials with 400 adults found a small but significant effect on overall sleep. The effect was bigger in people diagnosed with insomnia, at doses of 600 mg a day or more, and when people took it for at least eight weeks. Participants also reported feeling more alert on waking and less anxious.
The safety record is the catch. NCCIH notes rare cases of liver injury linked to ashwagandha supplements. It says to avoid it during pregnancy and breastfeeding, and that it isn’t recommended for people with thyroid or autoimmune disorders, hormone-sensitive prostate cancer, or surgery coming up. The meta-analysis authors also said there isn’t enough data to judge long-term safety.
L-theanine
Limited evidenceL-theanine is an amino acid found in tea. A 2025 review of 19 trials with 897 participants found it modestly improved self-reported time to fall asleep, daytime dysfunction and overall sleep quality. The authors flagged a big limitation: few of the studies tested L-theanine on its own rather than in a blend, so it’s hard to know what did the work. All the improvements were self-rated.
Lavender
Limited evidenceThe research is mostly on smelling lavender essential oil, not swallowing it. A recent meta-analysis of 11 randomized trials with 628 adults found that lavender aromatherapy improved sleep quality scores, though the authors said the number and quality of studies limit the conclusion. NCCIH also notes a few reports of breast tissue swelling in children who used topical lavender products, though it’s unclear the oil caused it.
Glycine
Weak evidenceGlycine is an amino acid, and its sleep research is a handful of small trials from Japan. In one of their trials, healthy volunteers whose sleep was cut by a quarter for three nights took 3 g of glycine or placebo before bed; the glycine group reported less fatigue the next day and did better on an attention test. Those are small studies of short-term effects, not tests in people with insomnia.
Valerian
Weak evidenceValerian root is a long-standing herbal sleep remedy, and the better trials keep finding small effects. In the main trial behind the AASM review, a valerian-hops combination shortened lab-measured time to fall asleep by about 9 minutes, below what the panel considered clinically meaningful, and people’s own sleep ratings didn’t improve to a meaningful degree. NCCIH says its value for insomnia has not been demonstrated and long-term safety is uncertain.
Chamomile
Weak evidenceA 2019 meta-analysis of 12 trials found pooled improvements in sleep quality scores, but the only trial that looked at insomnia itself found no change in insomnia severity. NCCIH’s summary is that there’s no conclusive evidence it helps. A cup of chamomile tea is still a reasonable part of a wind-down routine, as long as you aren’t allergic to ragweed or related plants, and as long as the extra fluid doesn’t wake you to pee.
Tart cherry
Weak evidenceThe enthusiasm traces to two small studies: a 2010 pilot in 15 older adults with insomnia and a 2012 trial in which 20 healthy volunteers drank tart cherry juice concentrate for a week and slept somewhat longer and better. Newer trials haven’t repeated it. A 2024 crossover trial in 34 adults with sleep problems found no effect on any sleep measure after two weeks of tart cherry capsules, and a 30-day trial of juice or capsules in 44 healthy adults found no difference in sleep time or quality.
Tryptophan and 5-HTP
Weak evidenceThe AASM recommends against tryptophan for chronic insomnia. The bigger issue is safety. NCCIH warns that L-tryptophan supplements may cause life-threatening serotonin toxicity when combined with medicines that affect serotonin, which includes many antidepressants. 5-HTP works on the same pathway, so the same caution applies.
CBD
Weak evidenceNCCIH found insufficient evidence to support cannabinoids for any sleep disorder, and notes CBD has been associated with liver injury and drug interactions. The FDA has concluded that CBD products are excluded from the legal definition of a dietary supplement, so CBD “sleep supplements” sit outside even the light rules that cover vitamins.
Kava
Weak evidenceVery little research has tested kava for insomnia, and NCCIH warns that kava use has been linked to liver injury that is sometimes serious or even fatal. Of everything on this list, it’s the one we’d tell you to skip outright.
What about Benadryl, ZzzQuil and Unisom?
These contain diphenhydramine or doxylamine, older antihistamines whose main side effect is drowsiness. They’re over-the-counter drugs, not supplements. The AASM reviewed trials of 50 mg diphenhydramine and found improvements in time to fall asleep and total sleep that fell below the level of clinical significance, so it suggests against it for chronic insomnia. MedlinePlus says diphenhydramine generally should not be used in older adults except for serious allergic reactions, and should not be used to make a child sleepy.
Before you buy any sleep supplement
- Ask a pharmacist about your medications. Interactions are the most common real risk, especially with antidepressants, blood thinners, seizure drugs, thyroid medicine and anything sedating.
- Pick one, not a blend. If a product combines six ingredients, you’ll never know which one helped, or which one caused a side effect.
- Look for a third-party seal, such as USP Verified. The FDA doesn’t approve dietary supplements before they go on sale, and the melatonin gummy findings show labels can be far off.
- Set a trial period and keep notes. Most of the trials above lasted between one and eight weeks. Log bedtime, roughly how long it took to fall asleep and how you felt the next day.
- Stop if nothing changes, and stop right away if you notice side effects. Ashwagandha, kava and CBD have all been linked to liver injury.
When to see a doctor
Talk to your doctor or pharmacist first if you:
- take prescription medicine, especially antidepressants, blood thinners, seizure medication, thyroid medication or sedatives
- are pregnant or breastfeeding, have liver, kidney or thyroid disease, or have surgery scheduled
- want to give any sleep aid to a child; ask your pediatrician
- have had trouble sleeping at least three nights a week for three months. That’s chronic insomnia, and cognitive behavioral therapy for insomnia (CBT-I) is the treatment the AASM strongly recommends.
- snore loudly, gasp at night or feel very sleepy during the day, which can point to sleep apnea
What works better than any supplement
The treatments with the strongest evidence for sleep don’t come in a bottle. CBT-I has a strong AASM recommendation, which no supplement has. The free pieces of it, like getting out of bed when you can’t sleep and keeping a fixed wake-up time, are ranked in how to fall asleep fast. Then work through the sleep hygiene checklist, or browse every guide in Supplements.
Common questions
What is the most effective supplement for sleep?
Melatonin has the most research, and it works best for body-clock problems like jet lag. For general insomnia its effect is modest, about 7 minutes faster to fall asleep in one meta-analysis, and no supplement has strong evidence.
Are natural sleep aids safe?
Not automatically. Kava and ashwagandha have been linked to liver injury, tryptophan can cause serotonin toxicity with some antidepressants, and supplement labels can be inaccurate. Ask a pharmacist before combining any with medication.
Does valerian root work for sleep?
The trials show small effects that fall below what matters clinically, and the American Academy of Sleep Medicine suggests against using it for chronic insomnia.
What works better than sleep supplements?
Cognitive behavioral therapy for insomnia (CBT-I) carries a strong recommendation from the American Academy of Sleep Medicine, which no supplement has.
Written and checked by the Sleep Brief editors. We base every article on published research and guidance from medical bodies, and link the sources inline. How we research.
This article is for general education and isn't medical advice. If poor sleep lasts more than a few weeks, or you snore loudly, stop breathing in your sleep or feel sleepy while driving, talk to a doctor.
