The best-supported use is delayed sleep phase syndrome. Probably helpful for general adult sleep onset or quality, sleep in children with neurodevelopmental conditions, shift-work sleep issues, and some secondary effects, but blood pressure, metabolic, and older-adult sleep findings look more mixed under the current grading system. Long-term tolerability now sits on the caution track.
What the research says
Each row is a different health effect. A means the support looks strongest, B likely helpful, C mixed or modest, and — not enough human evidence yet.
Papers are individual studies. Research reviews summarize evidence from multiple studies, such as systematic reviews and meta-analyses.
B · Likely helpful
B
Sleep onset & quality (general adults)
Reduces sleep onset latency. Dose-response benefit peaks around 4 mg/day.
40 papers · 20 research reviews
B
Sleep in children with ADHD or autism
Cleanest positive signal: 9 of 10 review-level papers report shorter sleep onset and longer total sleep time.
20 papers · 10 research reviews
B
Antioxidant & oxidative stress markers
Reduces inflammation and oxidative damage; raises the body's antioxidant capacity. Larger effects when used alongside cancer treatment.
52 papers · 32 research reviews
B
Delayed sleep phase syndrome
All 4 review-level papers positive: shorter sleep onset latency, more total sleep time. Small evidence base but clean direction.
10 papers · 4 research reviews
B
Sleep in shift workers
Reduces daytime sleepiness and sleep onset latency on days off. Limited number of trials; effects depend on shift type.
8 papers · 1 research review
B
Cancer adjuvant / chemotherapy side effects
Multiple meta-analyses report improved tumor response and reduced side effects, but heterogeneity is high and trials are small. Promising but not yet definitive.
23 papers · 7 research reviews
C · Mixed or limited evidence
C
Blood pressure & cardiovascular markers
Modest reduction in systolic BP, mainly from controlled-release formulations dosed at night.
Improves blood sugar markers in metabolic-syndrome and diabetic populations. Smaller, less consistent effects in healthy adults.
42 papers · 22 research reviews
C
Pre-operative anxiety
RCT-level evidence positive-leaning; review-level evidence weaker. Reasonable as adjuvant pre-medication.
31 papers · 11 research reviews
C
Sleep in older adults
Equal split between positive and null findings (9 each). Controlled-release formulations show stronger signals than immediate-release. Effect appears largest in adults with low endogenous melatonin.
24 papers · 4 research reviews
— · Not enough human evidence yet
—
Jet lag
Only 4 reviews in the database — not enough to grade. The 2015 review found melatonin probably reduces jet lag symptoms, but modern meta-analytic coverage is thin.
4 papers
Safety
Safety is graded separately from benefits. Read these cautions first, especially if you take medication or have a medical condition.
⚠ ConcerningThe human evidence points to a meaningful reason for caution.
⚠
Adverse events & long-term tolerability
Across 5 Cochrane reviews, 39 meta-analyses, and 21 systematic reviews, no consistent signal of harm. Most reported adverse events are mild and dose-related. Dependency language was rare across longer-duration trials.
85 papers · 65 research reviews
Quick facts
Dose, form and timing based on trials in the database.
Typical dose
3 mg/day — median across general-adult sleep trials
Best taken
Bedtime or 30–60 min before. Time between dose and intended sleep onset is itself a significant predictor of effect
Form
Immediate-release for sleep onset. Controlled-release (Circadin and similar) for older-adult sleep maintenance and nocturnal blood pressure
Common side effects
Morning drowsiness, headache, vivid dreams. Dose-related and reduced at lower doses (<3 mg)
Drug interactions
May interact with anticoagulants, immunosuppressants, and some antidepressants
Dose range in trials
0.3 mg – 10 mg/day for sleep; up to 20 mg/day in cancer-adjuvant and oxidative-stress trials
Dose-response surprise
Higher doses (3–10 mg) outperform physiologic doses (0.3–1 mg) for adult sleep — opposite of the "less is more" claim sometimes made. Effect plateaus around 4 mg/day
Quality-verified products
Products that pass third-party quality testing.
Product quality data coming soon
Product recommendations are being built from USP Verified, NSF Certified, and Labdoor test data. Products will only appear here after the supplement itself clears the evidence bar above — and only if the product passes third-party purity testing.
How we graded Melatonin
Grades come from 261 unique research papers indexed from PubMed — including 87 meta-analyses, 36 systematic reviews, and 138 randomized trials. Trials vary widely in dose (0.3–20 mg) and timing (bedtime vs. evening vs. split). Effect-size pooling is often heterogeneous. Where dose-response or timing-response data exists, it is captured in subgroup framing. Each supplement is graded by health effect using a certainty × effect matrix applied across PubMed evidence per health effect. Cochrane reviews and high-quality systematic reviews carry the most weight. From abstract-only data, "high certainty" is rare — most A grades come from moderate certainty plus consistent meaningful-positive evidence. See Methodology for full detail.