Melatonin
Research reviewed: Up until 03/2026
Melatonin is a dietary supplement with 14 published peer-reviewed studies involving 1,484 participants, researched for Sleep, Bone Health, Blood Pressure and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Sleep
StrongBone Health
ModerateBlood Pressure
ModerateBlood Sugar
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Sleep
To systematically review whether melatonin improves sleep quality — measured using the Pittsburgh Sleep Quality Index (PSQI), a validated questionnaire where lower scores indicate better sleep — in adults with various diseases.
Study Type
Meta-analysis of 23 Randomized Controlled Trials (RCTs)
Purpose
To systematically review whether melatonin improves sleep quality — measured using the Pittsburgh Sleep Quality Index (PSQI), a validated questionnaire where lower scores indicate better sleep — in adults with various diseases.
Dose
Study dose varied between 2 and 10 mg/day melatonin
Participants
Adults across 23 RCTs identified from 2,642 papers screened
Duration
3-24 weeks
Results
Melatonin had a statistically significant (p < 0.001) positive effect on sleep quality (PSQI score reduced by an average of 1.24 points). The significant benefit was most pronounced in people with respiratory diseases (2.20-point improvement) and metabolic disorders (2.74-point improvement), with more modest but still significant gains in those with primary sleep disorders (0.67-point improvement). Melatonin did not show significant sleep benefits in people with mental disorders or neurodegenerative diseases.
To investigate the effects of melatonin supplementation on sleep in hypertensive patients chronically treated with beta-blockers (medications that help lower blood pressure and slow the heart rate by blocking the effects of adrenaline)
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effects of melatonin supplementation on sleep in hypertensive patients chronically treated with beta-blockers (medications that help lower blood pressure and slow the heart rate by blocking the effects of adrenaline)
Dose
2.5 mg/day melatonin or placebo
Participants
16 hypertensive men and women aged 45-64 years
Duration
3 weeks
Results
Compared with placebo, 3 weeks of melatonin significantly improved several aspects of sleep. Total sleep time significantly increased by 36 minutes and sleep efficiency (the percentage of time in bed actually spent sleeping) significantly improved by 7.6%. The time it took to fall asleep (sleep onset latency) decreased by 14 minutes while Stage 2 sleep, an important phase of restorative sleep, significantly increased by 41 minutes. Notably, even after stopping melatonin, researchers observed that participants fell asleep 25 minutes significantly faster, suggesting a lasting carryover effect, and no rebound insomnia (worsening sleep after stopping the treatment) was observed.
To determine whether 3 mg fast-release melatonin taken 1 hour before bedtime improves sleep in middle-aged adults diagnosed with primary insomnia (insomnia with no known underlying medical cause).
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To determine whether 3 mg fast-release melatonin taken 1 hour before bedtime improves sleep in middle-aged adults diagnosed with primary insomnia (insomnia with no known underlying medical cause).
Dose
3 mg fast-release melatonin orally, 1 hour before bedtime nightly or placebo
Participants
97 consecutive middle-aged patients with primary insomnia from Tianlin community, Shanghai (51 melatonin, 46 placebo)
Duration
4 weeks
Results
Melatonin significantly reduced early wake time (waking up too early in the morning) by 30.63 minutes compared to placebo. Melatonin also significantly reduced the proportion of N2 sleep (a lighter stage of non-dream sleep, roughly equivalent to "light sleep") by 7.07%. However, melatonin did not significantly change other objective sleep measures including total sleep time, sleep onset latency (time to fall asleep), sleep efficiency, or wake time after sleep onset. Subjective sleep questionnaires (PSQI, ISI, Epworth) also showed no significant group differences. No serious adverse events were reported.
How They Measured It
Objective sleep was measured by polysomnography (PSG) — an overnight lab test recording brain waves, eye movements, heart rate and muscle activity — considered the gold standard for sleep measurement. Subjective sleep performance and excessive daytime sleepiness were assessed using the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), and Epworth Sleepiness Scale (ESS), which are validated questionnaires that measure perceived sleep quality, insomnia severity, and the level of daytime sleepiness or tendency to fall asleep during daily activities.
To assess whether 3 weeks of prolonged-release melatonin 2 mg (PR-melatonin; Circadin — a slow-release formulation designed to mimic the gradual overnight rise in natural melatonin) improves sleep quality and morning alertness in older primary insomnia patients aged 55 and over.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To assess whether 3 weeks of prolonged-release melatonin 2 mg (PR-melatonin; Circadin — a slow-release formulation designed to mimic the gradual overnight rise in natural melatonin) improves sleep quality and morning alertness in older primary insomnia patients aged 55 and over.
Dose
2 mg/night prolonged-release melatonin or placebo, 2 hours before bedtime
Participants
70 primary insomnia outpatients aged ≥55 years; multi-centre study (France and other EU sites)
Duration
3 weeks treatment + 1-week washout (to assess withdrawal/rebound effects)
Results
Compared to placebo, PR-melatonin supplementation significantly improved three key sleep outcomes measured by LSEQ: Quality of Sleep (QOS) score improved by -22.5 vs. -16.5 mm on a visual analogue scale (p = 0.047) — meaning patients reported noticeably better sleep quality; Quality of Night (the patient's overall rating of how good their night was) improved by 0.89 vs. 0.46 categorical units; and morning alertness/Behaviour Following Waking improved by -15.7 vs. -6.8 mm, meaning patients woke up feeling more refreshed. The improvements in Quality of sleep and morning alertness were strongly correlated (r = 0.77, p < 0.001), suggesting that individuals who reported better sleep quality also tended to experience higher levels of alertness upon waking. Crucially, no withdrawal effects were reported after stopping treatment — a significant advantage over many conventional sleep medications.
How They Measured It
Sleep parameters were measured using the Leeds Sleep Evaluation Questionnaire (LSEQ), a validated tool assessing four sleep-related domains including ease of falling asleep, quality of sleep, hangover, and morning alertness.
To investigate (1) whether older age or low endogenous melatonin production is a better predictor of who responds to prolonged-release melatonin (PRM), (2) whether 3-week efficacy is maintained over 6 months, and (3) the long-term safety profile.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate (1) whether older age or low endogenous melatonin production is a better predictor of who responds to prolonged-release melatonin (PRM), (2) whether 3-week efficacy is maintained over 6 months, and (3) the long-term safety profile.
Dose
2 mg/night prolonged-release melatonin (PRM/Circadin, a slow-release formulation designed to mimic the gradual overnight rise in natural melatonin) or placebo, 2 hours before bedtime
Participants
791 adult outpatients with primary insomnia, aged 18-80 years; enrolled at multiple primary care sites in Scotland, UK
Duration
2-week single-blind placebo run-in → 3-week double-blind PRM/placebo → 26-week continued treatment → 2-week washout
Results
In the 3-week double-blind phase, melatonin supplementation significantly reduced sleep latency (time to fall asleep) compared to placebo in elderly patients aged 65-80 years regardless of their melatonin levels: -19.1 min vs. -1.7 min reduction. This means elderly patients on melatonin fell asleep approximately 17 minutes faster than those on placebo. However, melatonin did not significantly reduce sleep latency in younger adults with low melatonin levels, suggesting that age — not simply low melatonin production — may be the key predictor of who responds. Over the 6-month extension, all sleep improvements (including sleep latency, sleep quality, quality of life, and clinician-rated global improvement) were maintained or enhanced, with no signs of tolerance developing. Adverse events were mild and did not differ clinically between melatonin and placebo.
To investigate the effects of repeated melatonin supplementation on sleep in hypertensive patients treated with beta-blockers (medications used to treat high blood pressure; some studies show that they suppress the body's natural nighttime melatonin production by blocking the enzyme that makes it — causing insomnia)
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effects of repeated melatonin supplementation on sleep in hypertensive patients treated with beta-blockers (medications used to treat high blood pressure; some studies show that they suppress the body's natural nighttime melatonin production by blocking the enzyme that makes it — causing insomnia)
Dose
2.5 mg/night melatonin or placebo
Participants
15 analysed (16 randomized; 1 removed for unstable medication dose); hypertensive patients aged 45-64 years (9 women) on atenolol or metoprolol (beta-blockers)
Duration
3 weeks
Results
Compared to placebo, researchers observed that melatonin significantly: increased total sleep time (TST) by +36 minutes (p = 0.046); improved sleep efficiency (the % of time in bed actually spent sleeping) by +7.6 percentage points (p = 0.046); shortened sleep onset latency to Stage 2 sleep (lighter but important restorative sleep) by -14 minutes (p = 0.001); and increased Stage 2 sleep duration by +41 minutes (p = 0.037). The night after stopping melatonin, sleep onset latency was still significantly shorter by 25 minutes. Melatonin did not alter mood, energy levels, or blood pressure significantly.
To test whether melatonin improves sleep onset (how quickly a person falls asleep after trying to sleep) in patients with Delayed Sleep Phase Disorder. Delayed Sleep-Wake Phase Disorder (DSWPD) is a circadian rhythm sleep disorder in which a person’s internal body clock is shifted later than normal, causing them to fall asleep and wake up much later than desired or socially expected.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To test whether melatonin improves sleep onset (how quickly a person falls asleep after trying to sleep) in patients with Delayed Sleep Phase Disorder. Delayed Sleep-Wake Phase Disorder (DSWPD) is a circadian rhythm sleep disorder in which a person’s internal body clock is shifted later than normal, causing them to fall asleep and wake up much later than desired or socially expected.
Dose
0.5 mg/night fast-release melatonin (a very low, physiologically-dosed amount) or placebo, taken 1 hour before the patient's desired bedtime, combined with behavioural sleep-wake scheduling for 4 weeks
Participants
116 randomised (62 males; mean age 29.0 years); diagnosed DSWPD adults from Australian outpatient clinics
Duration
1-week baseline + 4-week treatment
Results
Compared to placebo, researchers observed that melatonin significantly advanced sleep onset by 34 minutes, meaning patients fell asleep over half an hour earlier on melatonin. Sleep efficiency also significantly increased. Patient-reported outcomes significantly improved with melatonin: Sleep-Related Impairment (a validated scale measuring daytime impairment from poor sleep) decreased; insomnia severity (ISI score, p = 0.035) decreased; sleep quality index score post-treatment was lower (p = 0.037); and functional disability (p = 0.045) decreased. A clinically meaningful proportion of melatonin patients improved: 52.8% showed at least 'minimal improvement' on the clinical global impression scale vs. only 24.0% of placebo patients (p < 0.05). Side effects (light-headedness, daytime sleepiness, decreased libido) were similar between groups.
To evaluate whether 5 mg melatonin taken 30 minutes before daytime sleep significantly reduces sleep onset latency (time to fall asleep) and improves other subjective sleep parameters in shift-work nurses suffering from insomnia.
Study Type
Double-blind, randomised, placebo-controlled crossover trial
Purpose
To evaluate whether 5 mg melatonin taken 30 minutes before daytime sleep significantly reduces sleep onset latency (time to fall asleep) and improves other subjective sleep parameters in shift-work nurses suffering from insomnia.
Dose
5 mg melatonin tablet or placebo taken 30 minutes before desired night-time sleep after completing night shifts
Participants
86 shift-work nurses aged 24-46 years with insomnia disorders
Duration
Acute (single-dose)
Results
Researchers observed that acute supplementation with 5 mg of melatonin taken before nighttime sleep significantly reduced the time it took participants to fall asleep (sleep onset latency). Specifically, melatonin reduced sleep onset latency by 16 minutes compared to baseline. The nurses' also reported significantly improved sleep quality with melatonin treatment. However, melatonin did not significantly change the total amount of sleep time or the number of times they woke up during the night. This suggests that while melatonin may help shift workers initiate sleep more quickly, it may not impact other aspects of sleep like duration or awakenings.
How They Measured It
Subjective sleep quality was measured using three self-reported assessments: the Baseline Insomnia Parameters questionnaire, which measures baseline sleep problems such as difficulty falling asleep, maintaining sleep, and early morning awakenings; the Sleep Quality Scale, a questionnaire that assesses perceived sleep quality on a scale from 1 (very satisfied) to 5 (very unsatisfied); and Quantitative Sleep Questions that evaluate habitual nighttime sleep patterns, including sleep onset latency, number of nocturnal awakenings, and total sleep duration.
To investigate whether melatonin improves both sleep quality and occupational cognitive performance in shift workers diagnosed with sleep disorders.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate whether melatonin improves both sleep quality and occupational cognitive performance in shift workers diagnosed with sleep disorders.
Dose
5 mg immediate-release melatonin taken 30 minutes before the night-time sleep period after completing shifts
Participants
72 male and female shift workers equally assigned to melatonin (n=36) or placebo (n=36) groups
Duration
4 weeks
Results
After 4 weeks, researchers observed that melatonin significantly improved shortPSQI scores (sleep quality improved) and significantly reduced OCFQ scores (fewer cognitive failures at work) compared to placebo. A significant positive correlation was found between the reduction in shortPSQI scores (sleep improvement) and the reduction in OCFQ scores (cognitive improvement) over 1 week and 4 weeks — meaning workers who slept better made fewer cognitive errors at work. Interestingly, fatigue was reported more frequently in the placebo group than in the melatonin group, suggesting melatonin may have had an anti-fatigue effect.
How They Measured It
Sleep quality was measured using the short Pittsburgh Sleep Quality Index (shortPSQI), a validated self-report questionnaire that assesses overall sleep quality and common sleep disturbances over the previous month. Cognitive performance was assessed using the Occupational Cognitive Failure Questionnaire (OCFQ), a validated tool measuring self-reported cognitive failures in the workplace such as attention lapses, memory errors, and task errors that are relevant to job performance and safety.
To investigate the effect of 3 mg melatonin on sleep quality and cognitive function in patients undergoing hemodialysis. Hemodialysis patients are known to have severely disrupted circadian rhythms, low natural melatonin production, and a very high prevalence of sleep disorders affecting their quality of life and mortality risk.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate the effect of 3 mg melatonin on sleep quality and cognitive function in patients undergoing hemodialysis. Hemodialysis patients are known to have severely disrupted circadian rhythms, low natural melatonin production, and a very high prevalence of sleep disorders affecting their quality of life and mortality risk.
Dose
3 mg/night melatonin or placebo tablet orally, 30 minutes before bedtime
Participants
102 eligible male and female hemodialysis patients with an average age of 58 years
Duration
6 weeks
Results
Researchers observed that sleep quality (measured by PSQI — Pittsburgh Sleep Quality Index, where lower scores = better sleep; scores above 5 indicate clinical sleep problems) was significantly better in the melatonin group after treatment: average PSQI score 12.66 vs. 18.86 in the placebo group. This represents a clinically substantial gap — melatonin patients had a PSQI score 6.2 points lower, meaning better sleep quality. Cognitive function also significantly improved in the melatonin group compared to controls. No significant adverse events were reported.
Bone Health
To investigate whether nightly melatonin treatment for 1 year improves bone mineral density ( a measure of how dense and strong bones are) in postmenopausal women with osteopenia (a pre-osteoporosis condition where BMD is below normal but not yet at the fracture-risk threshold of osteoporosis)
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate whether nightly melatonin treatment for 1 year improves bone mineral density ( a measure of how dense and strong bones are) in postmenopausal women with osteopenia (a pre-osteoporosis condition where BMD is below normal but not yet at the fracture-risk threshold of osteoporosis)
Dose
1 mg/night (n = 20) or 3 mg/night (n = 20) melatonin, or placebo (n = 41); nightly for 1 year
Participants
81 postmenopausal osteopenic women with an average age of 63 years
Duration
1 year
Results
Compared to placebo, the researchers observed that the femoral neck BMD (the bone density at the upper part of the thigh bone, one of the most common fracture sites in osteoporosis) increased by 1.4% overall across melatonin groups (p < 0.05 vs. placebo), with a clear dose-dependent response (p < 0.01): the 1 mg/day group gained 0.5% BMD vs. 2.3% for the 3 mg/day group. In the 3 mg/day group specifically, tibial trabecular thickness (density of the inner spongy bone in the shin) significantly improved by 2.2%, and spinal volumetric BMD increased by 3.6%. Additionally, 24-hour urinary calcium excretion (a measure of how much calcium is being lost through urine) was reduced by 12.2% with 3 mg/day, suggesting melatonin may also help retain calcium. No significant differences were found in calciotropic hormones or standard bone markers between groups. The BMD gains, while modest, are comparable to those seen with some established osteoporosis treatments.
Blood Pressure
To investigate whether repeated bedtime melatonin intake lowers ambulatory blood pressure (BP measured continuously over 24 hours via a wearable monitor) in men with untreated essential hypertension. Essential hypertension = high blood pressure with no single identifiable cause, by far the most common form.
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To investigate whether repeated bedtime melatonin intake lowers ambulatory blood pressure (BP measured continuously over 24 hours via a wearable monitor) in men with untreated essential hypertension. Essential hypertension = high blood pressure with no single identifiable cause, by far the most common form.
Dose
2.5 mg/day melatonin orally or placebo, 1 hour before sleep; both single (acute) and repeated (3-week daily) dosing tested
Participants
16 male patients with mild-to-moderate untreated essential hypertension with an average age of 55 years
Duration
3 weeks for repeated dosing arm; acute arm = single dose
Results
Repeated (3-week) melatonin significantly reduced sleep-time SBP/DBP by 6 mmHg/4 mmHg compared to placebo. The day-night amplitudes (the natural rise and fall pattern) of both systolic and diastolic BP were enhanced by 15% and 25%, respectively — a sign of improved cardiovascular circadian rhythm. A single (acute) dose of melatonin had no effect on BP at nighttime. No effect on heart rate was observed.
To examine whether melatonin taken during a high-sodium diet (HSD) — which is known to raise blood pressure — reduces 24-hour ambulatory BP and BP responses to physiological stressors (isometric handgrip exercise, post-exercise ischemia, and the cold pressor test) in young adults with normal blood pressure
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To examine whether melatonin taken during a high-sodium diet (HSD) — which is known to raise blood pressure — reduces 24-hour ambulatory BP and BP responses to physiological stressors (isometric handgrip exercise, post-exercise ischemia, and the cold pressor test) in young adults with normal blood pressure
Dose
10 mg/day melatonin supplementation or placebo
Participants
22 participants (11 men / 11 women; average 26.5 years)
Duration
10 days
Results
Melatonin significantly reduced mean nighttime (sleep-time) blood pressure compared to placebo during the high-sodium diet condition. Specifically, nighttime mean arterial pressure (MAP — a combined measure of systolic and diastolic pressure representing average pressure throughout the cardiac cycle) was significantly lower in the melatonin group. However, melatonin did not significantly affect BP reactivity during any of the three stress tests (handgrip exercise, post-exercise ischemia, or cold pressor test), meaning it reduced resting nighttime BP but did not blunt the acute stress-induced BP rises. These findings suggest melatonin selectively targets resting nighttime BP rather than acute cardiovascular stress responses.
Blood Sugar
To determine whether melatonin supplementation for 12 weeks improves mental health parameters (sleep quality, depression, anxiety), glycemic control (blood sugar), cardiometabolic risk markers, and oxidative stress indicators in diabetic patients undergoing hemodialysis
Study Type
Randomised, double-blind, placebo-controlled trial
Purpose
To determine whether melatonin supplementation for 12 weeks improves mental health parameters (sleep quality, depression, anxiety), glycemic control (blood sugar), cardiometabolic risk markers, and oxidative stress indicators in diabetic patients undergoing hemodialysis
Dose
10 mg/day melatonin (2 x 5 mg) or placebo, taken 1 hour before bedtime
Participants
60 diabetic hemodialysis patients aged 18–80 years (30 melatonin, 30 placebo)
Duration
12 weeks
Results
Melatonin significantly improved sleep quality, depression symptoms, and anxiety compared to placebo. Metabolically, melatonin significantly reduced fasting blood glucose by 21.77 mg/dL, serum insulin by 1.89 μIU/mL, and HOMA-IR (a score measuring insulin resistance — lower is better) by 1.45 units, while increasing the QUICKI score (a measure of insulin sensitivity — higher is better) by 0.01 units. Inflammation was significantly reduced: high-sensitivity C-reactive protein (hs-CRP — a blood marker of inflammation) fell by 1.92 mg/L and malondialdehyde (MDA — a marker of cellular damage from oxidative stress) fell by 0.21 μmol/L. Total antioxidant capacity (the blood's overall ability to fight harmful free radicals) significantly increased by 253.87 mmol/L (p < 0.001).
Frequently Asked Questions
Common questions about Melatonin research
There are currently 14 peer-reviewed studies on Melatonin (Melatonin), involving 1,484 total participants. Research covers Sleep, Bone Health, Blood Pressure and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (14 human studies), and reported outcomes.
Melatonin has been researched for: Sleep, Bone Health, Blood Pressure, Blood Sugar. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 14 out of 14 studies are human trials. Human trials carry more weight in our evidence scoring system.
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