Set expectations first
No supplement out-performs the fundamentals of sleep: a consistent schedule, morning light, a cool dark room, and limiting caffeine and alcohol. Supplements can play a supporting role, but they're a small lever compared with sleep habits and stress management.
Melatonin: a timing aid, not a sedative
Melatonin is a hormone that signals nighttime. The evidence is best for jet lag and shifting sleep timing, and weaker for chronic insomnia — professional guidelines generally don't recommend it as a primary insomnia treatment [1]. Lower doses taken earlier in the evening usually suit its timing role better than large bedtime doses, and products are often mislabeled, so third-party testing helps.
Where the evidence is mixed
Valerian is popular, but research is mixed and the American Academy of Sleep Medicine recommends against it for chronic insomnia in adults [2]. Magnesium (often as glycinate) helps mainly when intake is low; it's well tolerated and a reasonable foundation [4].
Stress and calm
Ashwagandha has some evidence for stress and sleep, though quality varies — and NCCIH notes rare reports of liver injury linked to ashwagandha products, so stop and seek care if you notice symptoms like jaundice or abdominal pain [3]. L-theanine, glycine, and tart cherry have modest or emerging support; passionflower, lemon balm, magnolia bark, apigenin, chamomile, holy basil, and L-tryptophan range from traditional use to preliminary evidence.
Safety notes
Many sleep supplements can add to the sedating effect of alcohol or medications, and some interact with prescriptions — tell your clinician what you take. L-tryptophan affects serotonin and shouldn't be combined with antidepressants without medical guidance. Use children's sleep supplements only with a pediatrician [1][3].
