Melatonin is one of those supplements that seems to promise everything. Better sleep, lower blood pressure, weight loss, anti-ageing effects, cancer support. The claims have grown far beyond what the research actually supports. Here’s what we know, what we don’t, and what you should actually expect.

What is melatonin?

Melatonin is a hormone your pineal gland produces when darkness falls. American dermatologist Aaron Lerner identified and named it in 1958, initially interested in whether it affected skin pigmentation (it doesn’t, as it turns out).

Your body makes melatonin from tryptophan, an amino acid you get from food. Production ramps up as light fades and drops off when morning comes. This is why staring at your phone at midnight is such a terrible idea for sleep.

Beyond the pineal gland, melatonin appears in the retina, bone marrow, gut, skin and immune cells. Receptors for it are scattered throughout your body, which explains why researchers keep finding effects on systems that seem unrelated to sleep: reproduction, immune function, energy balance, even mood.

Melatonin also functions as an antioxidant, neutralising reactive oxygen and nitrogen species. Whether this matters at supplemental doses is another question.

When should you take melatonin and at what dose?

Start low. Take 0.5mg to 1mg about 30 minutes before bed. If that doesn’t work after a few nights, try 3mg to 5mg.

Here’s something counterintuitive: more melatonin doesn’t mean better sleep. Research suggests physiological doses (0.3mg to 1mg) often work as well as higher doses [1]. The goal is finding the smallest amount that helps, not loading up.

Does melatonin whiten skin?

No. Despite the similar names, melatonin and melanin are different things. Melanin is the pigment that colours your skin. Melatonin is a hormone that regulates your sleep-wake cycle.

A study looking at oral melatonin found no effect on human skin pigmentation [2]. If anyone’s selling you melatonin for skin lightening, they’re either confused or hoping you are.

What are the claimed benefits of melatonin?

I’ve gone through the research on 20 supposed benefits. Some hold up reasonably well. Many don’t.

1. IVF success rates

The theory is that melatonin’s antioxidant properties protect eggs from oxidative damage during retrieval and fertilisation.

A meta-analysis of 7 randomised controlled trials found oral melatonin during IVF treatment increased the number of mature eggs and showed a trend toward higher clinical pregnancy rates, though the pregnancy rate difference wasn’t statistically significant [3].

It’s promising but not definitive. The sample sizes were small.

2. Weight control

A systematic review of 23 trials found melatonin supplementation (3mg to 10mg daily for 3 to 48 weeks) reduced body weight compared to placebo [4]. However, it didn’t affect BMI or waist circumference.

I’m sceptical about how meaningful this is. Weight dropped but body composition measures didn’t change? The practical benefit seems limited.

3. Pre-surgery anxiety

This one has decent evidence. A Cochrane review of 27 trials involving over 2,300 surgical patients found melatonin tablets or sublingual doses reduced preoperative anxiety when measured 50 to 120 minutes after dosing [5].

The effect was comparable to benzodiazepines but without the same sedation hangover. If you’re facing surgery and feeling anxious, this is worth discussing with your anaesthetist.

4. COVID-19 support

A small trial of 74 hospitalised patients with mild to moderate COVID-19 found that adding melatonin to standard care improved symptoms like cough, breathlessness and fatigue compared to standard care alone [5]. Patients also left hospital faster.

One small trial isn’t definitive. But it’s interesting given melatonin’s anti-inflammatory properties.

Up to 89% of children with autism have sleep problems. These can worsen behaviour and make everything harder for families.

A meta-analysis of 5 randomised trials in children with autism found melatonin improved sleep duration and the time it took to fall asleep [5]. Side effects were minimal. Few treatments in this population have such a favourable risk-benefit profile.

6. Postoperative pain and opioid use

A meta-analysis of 15 trials with over 1,100 participants showed melatonin slightly reduced postoperative pain scores and decreased the number of patients needing extra painkillers [5].

The word “slightly” matters here. The effect was real but modest. Don’t expect melatonin to replace proper pain management.

7. Inflammation

Melatonin supplementation significantly reduced TNF-α and IL-6 (inflammatory markers) compared to placebo in a meta-analysis of 13 trials [5]. The effect was stronger at doses of 10mg or more taken for at least 12 weeks.

Whether this translates to clinical benefit for inflammatory conditions remains unclear.

8. Migraine prevention

A meta-analysis of 25 trials in nearly 4,500 migraine patients found oral melatonin reduced attack frequency [5]. The best results came from 3mg taken at bedtime.

If you get frequent migraines, this is relatively cheap and low-risk to try alongside standard preventive treatments.

9. Primary insomnia

A meta-analysis of 19 placebo-controlled trials involving nearly 1,700 patients with primary insomnia found melatonin reduced time to fall asleep, increased total sleep time and improved overall sleep quality [5].

The NHS recommends melatonin for insomnia, particularly in adults over 55 [6]. It’s less powerful than prescription sleeping pills but causes fewer side effects.

If you have nocturia disrupting your sleep, melatonin might help you get back to sleep after bathroom trips, though it won’t reduce how often you need to go.

10. Secondary insomnia

When sleep problems stem from other conditions (pain, thyroid issues, reflux, lung disease, kidney problems, Parkinson’s), they’re called secondary insomnia.

A meta-analysis of 7 trials found melatonin reduced time to fall asleep and increased total sleep time, though it didn’t improve sleep efficiency [7].

For people with interstitial cystitis or overactive bladder where nighttime symptoms disrupt sleep, melatonin might help with sleep consolidation even if it doesn’t address the underlying bladder issue.

11. Non-alcoholic fatty liver disease

A meta-analysis of 5 trials found melatonin (6mg to 18mg daily for 4 to 56 weeks) reduced liver enzymes AST, ALP and GGT in people with fatty liver disease [8].

The sample sizes were small. This is preliminary, not practice-changing.

12. Blood pressure

A meta-analysis of 5 trials found oral melatonin reduced systolic blood pressure by about 3.4 mmHg and diastolic by about 3.3 mmHg [9].

That’s not dramatic, but it’s comparable to some lifestyle interventions. If you have diabetic bladder dysfunction and are also managing blood pressure, this might be worth mentioning to your doctor.

13. Fibromyalgia

About 75% of people with fibromyalgia have significant sleep problems, and poor sleep worsens pain.

A systematic review of 4 trials found melatonin improved pain levels, sleep quality and fibromyalgia impact scores [10]. Results were inconsistent for anxiety, fatigue and depression.

14. Blood lipids

A meta-analysis of 12 trials found melatonin improved LDL cholesterol and triglyceride levels [11].

I wouldn’t take melatonin primarily for cholesterol. But if you’re taking it for sleep and your lipids happen to be borderline, that’s a potential secondary benefit.

15. Blood sugar control

This is where things get complicated. Some studies show melatonin improves fasting glucose and insulin sensitivity [11]. Others show nothing.

The catch: melatonin receptors on pancreatic beta cells means it directly affects insulin secretion. Some genetic variants in melatonin receptor genes are associated with type 2 diabetes risk. The relationship between melatonin supplementation and blood sugar isn’t straightforward.

16. Cancer treatment support

I need to be careful here. Melatonin is not a cancer treatment.

A meta-analysis of 20 trials found adding melatonin to chemotherapy, radiotherapy or supportive care improved tumour response rates and overall survival [11]. It also reduced side effects like neurotoxicity, low platelet counts and weakness.

The authors flagged possible publication bias. Melatonin should never replace oncology treatment, but it might help manage treatment side effects. Discuss with your oncologist.

17. Jet lag

This is where melatonin shines. A Cochrane review concluded it’s “remarkably effective” for preventing or reducing jet lag when taken close to target bedtime [12].

It works best for eastward travel across 5 or more time zones. Take 0.5mg to 5mg at bedtime for the first few days after arrival. Westward travel generally causes less jet lag and needs less intervention.

18. Mood disorders

Here’s an area where melatonin disappoints. A systematic review found no evidence that melatonin significantly improves depression or seasonal affective disorder [13].

Agomelatine, a prescription antidepressant that acts on melatonin receptors, does work for depression. But taking melatonin supplements isn’t the same thing.

19. Pain relief

A meta-analysis of 19 trials found melatonin reduced pain intensity across various types: surgical pain, inflammatory pain, procedural pain [14]. It also reduced patients’ need for painkillers.

The mechanism likely involves melatonin’s interaction with opioid receptors and pain signalling pathways. This isn’t powerful enough to treat serious pain, but it might contribute as part of a multimodal approach.

20. Alzheimer’s disease

Sleep disturbances are common in Alzheimer’s, affecting up to 45% of patients. Nighttime wandering and daytime drowsiness exhaust carers and can accelerate cognitive decline.

A meta-analysis of 7 trials found melatonin increased total nighttime sleep in Alzheimer’s patients [15]. It didn’t improve cognition, but better sleep is valuable in itself for both patients and families.

Side effects

For most adults, short-term melatonin use appears safe. The NHS notes these possible side effects [6]:

Headache
Dizziness
Nausea
Drowsiness (which is rather the point)
Vivid dreams or nightmares

Some people report more lucid dreams on melatonin. This isn’t harmful unless the dreams disturb you.

Long-term safety data is limited because most studies lasted only weeks. A population study found long-term use of melatonin and sleep aids like zolpidem may be associated with increased fracture risk [16]. Another study found melatonin might increase reactive aggression [17].

18 safety precautions and drug interactions

Who should avoid melatonin

Pregnant women - Melatonin crosses the placenta and safety data is lacking.
Breastfeeding mothers - Same issue with unknown transfer to breast milk.
Children - The NHS advises against use in children unless prescribed by a specialist.
People with liver disease - Your liver metabolises melatonin, so impaired function means unpredictable levels.
People with kidney disease - Excretion may be affected, leading to accumulation.
Those with autoimmune conditions - Melatonin may stimulate the immune system.

Drug interactions

Blood pressure medications - Melatonin lowers blood pressure. Combined with nifedipine or other antihypertensives, this could cause excessive drops.
Blood thinners and NSAIDs - Melatonin may slow clotting. Avoid combining with warfarin, aspirin, clopidogrel, ibuprofen, naproxen, heparin or enoxaparin without medical advice.
Diabetes medications - Melatonin affects blood glucose. If you take insulin, metformin, glimepiride, glyburide or other diabetes drugs, monitor your levels more carefully.
Immunosuppressants - Because melatonin may enhance immune function, it could reduce the effectiveness of cyclosporine, tacrolimus, azathioprine, mycophenolate, sirolimus or corticosteroids.
Sedatives and sleeping pills - Combining melatonin with benzodiazepines (diazepam, lorazepam, clonazepam) or other sleep medications (zolpidem) increases drowsiness.
Fluvoxamine - This antidepressant significantly increases melatonin levels by blocking its breakdown. Adding supplements could cause excessive effects.
Contraceptive pills - Oral contraceptives already increase natural melatonin production. Adding supplements may lead to higher than expected levels.
Caffeine - Reduces melatonin levels, potentially undermining supplementation. Afternoon coffee may still be affecting your melatonin at bedtime.
Verapamil - This calcium channel blocker may reduce melatonin’s effectiveness.
Flumazenil - This benzodiazepine reversal agent may block melatonin’s effects.

Practical precautions

Don’t drive after taking it - This should be obvious but apparently needs stating.
More isn’t better - Higher doses don’t improve effectiveness and may cause more side effects. Some people do better on 0.5mg than 5mg.

The bottom line

Melatonin works well for jet lag and circadian rhythm problems. For general insomnia, effects are real but modest. For most other claimed benefits, the evidence is preliminary or weak.

It’s not a sleeping pill in the traditional sense. It signals to your body that it’s time for sleep rather than forcing unconsciousness. If your problem is circadian misalignment (shift work, jet lag, delayed sleep phase), melatonin makes sense. If you’re lying awake anxious at 2am despite normal circadian rhythm, addressing the anxiety might work better.

If melatonin doesn’t help, other options include valerian, L-theanine, GABA or magnesium. Each works through different mechanisms.

12 benefits and side effects of melatonin - our other melatonin article with additional detail
5 alternative therapies for insomnia
18 benefits and side effects of probiotics

References

Ferracioli-Oda E, Qawasmi A, Bloch MH. Meta-analysis: melatonin for the treatment of primary sleep disorders. PLoS One. 2013;8(5):e63773.
McElhinney DB, Hoffman SJ, Robinson WA, Ferguson J. Effect of melatonin on human skin color. J Invest Dermatol. 1994;102(2):258-259.
Espino J, Macedo M, Lozano G, et al. Impact of melatonin supplementation in women with unexplained infertility undergoing fertility treatment. Antioxidants (Basel). 2019;8(9):338.
Mostafavi SA, Akhondzadeh S, Mohammadi MR, et al. The effect of melatonin supplementation on body weight: a systematic review and meta-analysis. J Pediatr Endocrinol Metab. 2021;34(10):1219-1227.
Andersen LP, Gögenur I, Rosenberg J, Reiter RJ. The Safety of Melatonin in Humans. Clin Drug Investig. 2016;36(3):169-175.
NHS. Melatonin for sleep problems. Available at: https://www.nhs.uk/medicines/melatonin/
Li T, Jiang S, Han M, et al. Exogenous melatonin as a treatment for secondary sleep disorders: A systematic review and meta-analysis. Front Neuroendocrinol. 2019;52:22-28.
Pakravan H, Ahmadian M, Fani A, et al. The Effects of Melatonin in Patients with Nonalcoholic Fatty Liver Disease: A Randomized Controlled Trial. Adv Biomed Res. 2017;6:40.
Grossman E, Laudon M, Zisapel N. Effect of melatonin on nocturnal blood pressure: meta-analysis of randomized controlled trials. Vasc Health Risk Manag. 2011;7:577-584.
de Zanette SA, Vercelino R, Laste G, et al. Melatonin analgesia is associated with improvement of the descending endogenous pain-modulating system in fibromyalgia. BMC Pharmacol Toxicol. 2014;15:40.
Mohammadi-Sartang M, Ghorbani M, Mazloom Z. Effects of melatonin supplementation on blood lipid concentrations: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2018;37(6 Pt A):1943-1954.
Herxheimer A, Petrie KJ. Melatonin for the prevention and treatment of jet lag. Cochrane Database Syst Rev. 2002;(2):CD001520.
Hansen MV, Danielsen AK, Hageman I, et al. The therapeutic or prophylactic effect of exogenous melatonin against depression and depressive symptoms: a systematic review and meta-analysis. Eur Neuropsychopharmacol. 2014;24(11):1719-1728.
Andersen LP, Werner MU, Rosenberg J, et al. A systematic review of peri-operative melatonin. Anaesthesia. 2014;69(10):1163-1171.
McCleery J, Cohen DA, Sharpley AL. Pharmacotherapies for sleep disturbances in dementia. Cochrane Database Syst Rev. 2016;11(11):CD009178.
Wichniak A, Jankowski KS, Skalski M, et al. Risk of Bone Fractures with Hypnotics: An Updated Meta-Analysis. J Clin Med. 2021;10(7):1543.
Bromundt V, Wirz-Justice A, Boutellier M, et al. Effects of a dawn-dusk simulation on circadian rest-activity cycles, sleep, mood and well-being in dementia patients. Exp Gerontol. 2019;124:110641.