Key Takeaways
- Melatonin works best for timing issues (jet lag, shift work)—not general insomnia. Start with 0.5-1mg, not 10mg
- Magnesium has decent evidence, especially magnesium glycinate. Works better if you're deficient
- L-theanine is promising for anxiety-related sleep issues but not a knockout solution
- Most herbal supplements (valerian, passionflower) have weak and inconsistent evidence
- Behavioral changes (CBT-I) consistently outperform supplements for chronic insomnia
The sleep supplement aisle is overwhelming. Melatonin, magnesium, valerian, CBD, ashwagandha, GABA, L-theanine, passionflower... all promising better sleep. But how many actually have evidence behind them?
I've tried most of these—some out of desperation at 3am, others on the recommendation of well-meaning friends. After years of personal experimentation and reading the research, here's an honest ranking.
01 How We Ranked These
We looked at three factors for each supplement:
Evidence Quality
How many randomized controlled trials exist? How large were they? Were results replicated?
Effect Size
Even if statistically significant, is the real-world effect meaningful? 5 minutes faster sleep onset isn't life-changing.
Safety Profile
What are the known side effects? Interactions? Long-term unknowns?
02 Tier A: Solid Evidence
These supplements have multiple well-designed studies supporting their use for sleep in specific contexts.
Melatonin
Tier AMelatonin is your body's natural "darkness hormone." Supplementing it doesn't make you sleepy like a sedative—it signals to your brain that it's time to sleep.
Best For
- Jet lag recovery[1]
- Shift work adjustment
- Delayed sleep phase (night owls who can't sleep early)
- Older adults (melatonin production declines with age)
Less Effective For
- General insomnia (staying asleep issues)
- Sleep quality improvement
- Anxiety-related sleep problems
Dosage Notes
Less is more. Most supplements are vastly overdosed. Studies show 0.5-1mg is often as effective as 5-10mg, with fewer side effects[2]. Higher doses can cause morning grogginess and may desensitize receptors over time.
Timing matters: Take 1-2 hours before desired sleep time, not right at bedtime.
Side Effects
Generally safe short-term. May cause vivid dreams, morning grogginess (if overdosed), headaches. Long-term effects not well studied.
Magnesium
Tier AMagnesium is involved in hundreds of bodily processes, including regulating neurotransmitters that calm the nervous system. Deficiency is common and often undiagnosed.
Best For
- Those with low magnesium levels (common in Western diets)
- Restless legs syndrome
- Muscle relaxation before bed
- Stress-related sleep issues[3]
Form Matters
- Magnesium glycinate: Best absorbed, most calming
- Magnesium citrate: Good absorption, may have laxative effect
- Magnesium oxide: Cheap but poorly absorbed
- Magnesium L-threonate: Crosses blood-brain barrier, pricier
Dosage Notes
200-400mg of elemental magnesium before bed. Start low to assess tolerance. Glycinate and threonate forms are preferred for sleep.
Side Effects
Generally safe. High doses may cause digestive issues (especially citrate/oxide). May interact with antibiotics and blood pressure medications.
03 Tier B: Promising Evidence
These have positive research but either smaller studies, mixed results, or work for specific subgroups.
L-Theanine
Tier BAn amino acid found in tea leaves. Promotes relaxation without sedation by increasing alpha brain waves and GABA[4].
Best For
- Racing thoughts at bedtime
- Anxiety-related sleep onset issues
- Combining with caffeine (counteracts jitters)
Key Research
Studies show improved sleep quality in people with anxiety and ADHD. Effects are subtle—don't expect knockout power.
Dosage Notes
100-400mg before bed. Can be taken during the day for general calm without drowsiness.
Glycine
Tier BAn amino acid that may lower core body temperature (a sleep trigger) and act on calming neurotransmitter systems[5].
Best For
- Improving subjective sleep quality
- Reducing next-day fatigue
- Those who run hot at night
Key Research
Japanese studies show improved sleep quality scores and less daytime fatigue. Limited Western replication.
Dosage Notes
3g before bed. Has a slightly sweet taste; can be dissolved in water.
Ashwagandha
Tier BAn Ayurvedic adaptogen that reduces cortisol and anxiety. Sleep benefits are likely secondary to stress reduction[6].
Best For
- Stress-related sleep problems
- Those with elevated cortisol
- General anxiety affecting sleep
Caution
Avoid if you have thyroid issues (may affect thyroid hormones). Not for pregnant/nursing women.
Dosage Notes
300-600mg of root extract standardized to withanolides, taken in evening. Effects build over weeks.
04 Tier C: Weak or Inconsistent Evidence
These are popular but have limited quality research supporting their use for sleep.
Valerian Root
Mixed ResultsOne of the most studied herbal sleep aids, but results are inconsistent. Some trials show modest benefits; others show no difference from placebo. May take 2-4 weeks to work. Notable for its unpleasant smell[7].
Passionflower
Limited StudiesSome evidence for anxiety reduction. Few quality studies on sleep specifically. Often combined with other herbs, making it hard to isolate effects.
GABA (Oral)
Absorption IssuesGABA is the main inhibitory neurotransmitter, but oral GABA doesn't cross the blood-brain barrier well. Some studies show stress reduction, but sleep-specific evidence is weak.
Chamomile
Mild at BestTraditional use for relaxation, but clinical evidence for sleep is minimal. May provide a relaxing ritual more than pharmacological effect. Safe as tea.
Lavender (Oral)
Anxiety, Not SleepSilexan (lavender oil capsules) has evidence for anxiety, but direct sleep evidence is limited. Aromatherapy lavender shows some promise but studies are low quality.
05 Tier D: Skip These
Popular products with little evidence, safety concerns, or better alternatives.
Diphenhydramine (Benadryl, ZzzQuil)
Not a supplement, but widely used for sleep. Causes next-day cognitive impairment, tolerance develops quickly, and it's been linked to dementia risk with long-term use[8]. Not recommended for regular sleep use.
Kava
Has evidence for anxiety but significant liver toxicity concerns. Banned or restricted in several countries. The risk isn't worth it when safer options exist.
5-HTP
Serotonin precursor—sounds logical, but evidence for sleep is minimal. Potential for serotonin syndrome if combined with SSRIs or other serotonergic drugs.
CBD
Extremely popular but evidence is weak and inconsistent. Studies use high doses (300mg+) far exceeding typical products. May help anxiety, which could indirectly help sleep, but don't expect miracles.
"The best predictor of whether a supplement 'works' is whether you believe it will. Placebo effects in sleep studies are enormous."
— Dr. Michael Grandner, Sleep Researcher
06 Safety Notes
Supplements Aren't Regulated Like Drugs
What's on the label may not match what's in the bottle. Use brands with third-party testing (NSF, USP, ConsumerLab).
Drug Interactions Are Real
Many sleep supplements interact with blood thinners, sedatives, antidepressants, and other medications. Always check with a pharmacist.
Don't Stack Without Guidance
Taking multiple sedating supplements together can amplify effects unpredictably. Start with one at a time.
Address the Root Cause
Supplements are band-aids. If you have chronic insomnia, CBT-I (cognitive behavioral therapy for insomnia) is more effective than any supplement.
The Bottom Line
Most sleep supplements are overhyped. Melatonin works for timing issues, not general insomnia—and lower doses are better. Magnesium is worth trying if you don't get enough from food. L-theanine may help anxiety-driven sleep problems.
Everything else? The evidence is weak, inconsistent, or both. Herbal supplements like valerian and passionflower have centuries of traditional use but limited clinical support.
If you've been struggling with sleep for more than a few weeks, the answer probably isn't in a bottle. Consider talking to a sleep specialist about CBT-I, which has stronger evidence than any supplement on this list.
Sources & Further Reading
- "Melatonin for the prevention and treatment of jet lag." Cochrane Database of Systematic Reviews. (2002) PubMed →
- "Evidence for the efficacy of melatonin in the treatment of primary adult sleep disorders." Sleep Medicine Reviews, 34, 10-22. (2017) PubMed →
- "The effect of magnesium supplementation on primary insomnia in elderly." Journal of Research in Medical Sciences, 17(12), 1161-1169. (2012) PubMed →
- "GABA and l-theanine mixture decreases sleep latency and improves NREM sleep." Pharmaceutical Biology, 57(1), 65-73. (2019) PubMed →
- "New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep." Journal of Pharmacological Sciences, 118(2), 145-148. (2012) PubMed →
- "Efficacy and Safety of Ashwagandha Root Extract in Insomnia and Anxiety." Cureus, 11(9), e5797. (2019) PubMed →
- "Valerian for sleep: a systematic review and meta-analysis." American Journal of Medicine, 119(12), 1005-1012. (2006) PubMed →
- "Cumulative use of strong anticholinergics and incident dementia." JAMA Internal Medicine, 175(3), 401-407. (2015) PubMed →
Recommended Resources
- Examine.com - Sleep Supplements Guide (evidence-based analysis)
- ConsumerLab.com - Third-party testing of supplements
- Why We Sleep by Matthew Walker (Chapter on sleep aids)
