Melatonin is one of the most popular sleep supplements in the United States, but it is widely misunderstood. It is not a sedative like diphenhydramine or prescription Z-drugs. It is a hormone that tells your brain what time of day it is. That difference determines how, when, and how much you should use it.
**What melatonin actually does.** Your pineal gland releases melatonin in response to darkness. Levels rise in the evening, peak in the middle of the night, and fall toward morning. This signal helps shift your circadian clock into night mode. Taking melatonin works best when your internal clock is misaligned — jet lag, delayed sleep phase, or shift work — not when you simply cannot fall asleep because of stress or anxiety.
**Effective doses are lower than most bottles suggest.** For circadian timing, 0.3–1 mg taken several hours before the desired bedtime is often more effective than 3–10 mg. Higher doses can oversaturate melatonin receptors, causing grogginess, vivid dreams, or a hangover effect the next day. The American Academy of Sleep Medicine notes that long-term safety data for adults is limited and that more is not better.
**Timing matters more than dose.** For shifting your clock earlier, take 0.5–1 mg about 4–6 hours before your target bedtime. For jet lag, take 0.5–5 mg at bedtime in the new time zone for the first few nights. For general insomnia, melatonin has modest benefit at best; behavioral treatments like CBT-I are more effective.
**Who should be cautious or avoid it.** Pregnant or breastfeeding people, children, and people with autoimmune conditions, seizure disorders, depression, or who take blood thinners, blood-pressure medications, diabetes medications, or immunosuppressants should talk to a clinician first. Melatonin can interact with several common drugs. Do not combine it with alcohol or other sedatives.
**Quality control is a real problem.** A 2017 study in the Journal of Clinical Sleep Medicine found that melatonin supplements varied from 83% less to 478% more than the labeled dose. Look for products certified by USP, NSF, or ConsumerLab. Avoid gummies with inconsistent dosing and high sugar content.
**Side effects to watch for.** Headache, dizziness, nausea, daytime drowsiness, and vivid dreams are the most common. If you feel groggy the next morning, the dose was too high or the timing was too late. Lower the dose or take it earlier.
**Better alternatives for true insomnia.** If your problem is not a misaligned clock, melatonin is unlikely to help much. Cognitive behavioral therapy for insomnia (CBT-I), consistent wake times, morning light exposure, and a cool, dark, quiet bedroom address the root causes better than any supplement.