How long does Melatonin last?

Melatonin is a hormone produced by the pineal gland that helps regulate the sleep–wake cycle. As an over‑the‑counter supplement, it is used to ease jet lag, shift work sleep issues, and some forms of insomnia. Melatonin has a half‑life of about 20–45 minutes, depending on the formulation, and is cleared after roughly 4–5 half‑lives. Standard immediate‑release melatonin therefore remains active for about 4–5 hours. Extended‑release products can last longer by releasing melatonin gradually.

How melatonin works

Natural melatonin levels rise about two hours before bedtime, signaling the body that it is time to sleep. Light exposure inhibits melatonin production, helping you stay awake. Supplemental melatonin boosts these levels to encourage drowsiness.

How long until it kicks in?

Melatonin is absorbed quickly, with blood levels peaking in about one hour. For most people, taking it 30–60 minutes before desired sleep time helps onset of drowsiness. Immediate‑release forms act faster, while extended‑release may aid those who wake during the night.

Side effects

  • Daytime sleepiness or fatigue
  • Dizziness
  • Headache
  • Nausea
  • Anxiety
  • Vivid or unusual dreams
  • Lowered blood pressure

Best practices and timing

  • Take 30 minutes to 2 hours before bedtime
  • Use good sleep hygiene: dim lights, limit screens, maintain consistent sleep schedule
  • Expose yourself to daylight early to reinforce natural rhythms
  • Avoid caffeine and alcohol in the evening

Who should avoid melatonin?

Consult a healthcare provider before use if you are pregnant or breastfeeding, have an autoimmune disorder, seizures, heart or kidney disease, depression, or take immunosuppressants, hormone therapy, diabetes or blood pressure medications, or anticoagulants.

Sources

  • Melatonin: What You Need To Know. National Institutes of Health.
  • Auld F et al. Efficacy of melatonin in adult sleep disorders. Sleep Medicine Reviews. 2017;34:10‑22.
  • Melatonin. StatPearls. Updated 2024 Feb.
  • About Sleep. Centers for Disease Control and Prevention.
  • Costello RB et al. Effectiveness of melatonin for healthy sleep. 2014.