How we ranked
Each supplement is scored on quality of randomized trials, effect size (sleep onset, total sleep time, quality), and safety profile. We separate 'evidence for circadian phase shifting' from 'evidence for primary insomnia' — they are different uses.
Tier S: melatonin (low dose, right timing)
0.3 to 1 mg taken 4 to 6 hours before target bedtime is the most evidence-backed circadian intervention. It is NOT a sleep aid for primary insomnia — most consumer doses (5 to 10 mg) are far too high and produce next-day grogginess without benefit.
Tier A: magnesium glycinate
200 to 400 mg, 60 minutes before bed. Multiple trials show modest improvement in sleep quality and onset, especially in adults with low dietary magnesium. Well tolerated; glycinate form avoids GI side effects.
Tier A: l-theanine
200 mg before bed. Reduces sleep onset latency and improves subjective sleep quality through GABA modulation. Most useful when anxiety drives insomnia.
Tier B: glycine
3 grams before bed. Several Japanese trials show improved sleep quality and reduced daytime fatigue. Slight body cooling effect helps initiate sleep.
Tier B: ashwagandha
300 to 600 mg KSM-66 extract. Reduces cortisol; modest sleep improvement in trials. Best for stress-driven insomnia.
Tier B: valerian
300 to 600 mg of standardized extract. Mixed evidence; works for some, no effect for others. Strong odor and rare liver concerns.
Tier C: GABA, 5-HTP, tryptophan
Theoretically interesting; trial evidence weak or inconsistent. Try only after stronger options.
Tier D: CBD
Sleep claims outpace evidence. Some trials show benefit at high doses (>150 mg) but quality control and cost are issues.
Avoid for routine use: diphenhydramine
Benadryl/ZzzQuil. Tolerance builds in days, reduces deep sleep, impairs cognition next day. Linked in observational studies to long-term cognitive decline. Do not use chronically.
What we recommend trying first
If anxiety dominates: l-theanine + magnesium glycinate. If circadian drift (late bedtime drift): low-dose melatonin 5 hours before target bedtime + morning bright light. If general stress and tension: magnesium glycinate + ashwagandha. Reassess after 2 to 4 weeks.
FAQ
Are supplements regulated? In the US, no — quality varies dramatically. Buy from brands with USP, NSF, or ConsumerLab certification. Can I combine them? Most are safe to stack at standard doses, but always check with your pharmacist or clinician, especially if you take prescription meds.