Is It Safe to Take Melatonin Every Night? (UK Guide)
- Phoebe Walsh
- 2 days ago
- 5 min read
Melatonin is one of the most widely used sleep aids globally, but is it safe to take every night?
And how does that apply to the UK, where melatonin is only available via prescription?
In this guide, we answer these questions and more, drawing on the latest scientific research and input from doctors.
What Is Melatonin?
Melatonin is a hormone naturally produced by the pineal gland in the brain. It plays a central role in regulating the circadian rhythm, the body’s internal clock that governs sleep and wake cycles. Melatonin levels usually rise in the evening as light levels fall, helping the body prepare for sleep, then drop again in the morning to support waking and alertness.
Supplemental melatonin is designed to replicate this natural process and is commonly used to support sleep in specific situations, including jet lag, shift work sleep disorder, delayed sleep phase disorder, and, in some cases, short-term insomnia. Regulatory treatment varies by country. In the United States and Canada, melatonin is widely available over the counter, whereas in the UK it is classified as a prescription-only medicine.
Is Melatonin Available Over the Counter in the UK?
No. As of 2026, melatonin is not legally available over the counter in the UK. While some brands like Lemme Sleep might appear available, it is classified by the MHRA (Medicines and Healthcare products Regulatory Agency) as a prescription-only medication.
NHS guidance generally restricts melatonin prescriptions to short-term use in specific populations, such as:
Children and adolescents with sleep disorders related to conditions like ADHD or autism
Adults over 55 with primary insomnia (for up to 13 weeks)
Some private clinics and online pharmacies may offer melatonin, but this should only be done under medical supervision.
Is It Safe to Take Melatonin Every Night?
This depends on several factors, including dosage, duration, age, and whether the supplement is being taken under medical advice.
Short-Term Safety
Most research suggests that short-term use of melatonin is generally safe for most people. When side effects do occur, they are usually mild and transient, commonly including drowsiness, dizziness, headaches, or nausea.
In the UK, both NHS and NICE support limited-duration use of melatonin in appropriate clinical situations, particularly for older adults and for individuals with diagnosed circadian rhythm sleep disorders.
Long-Term Safety: What the Research Says
“In the short term, we’ve seen melatonin generally well-tolerated with few short-term side effects — things like dizziness, headache, or daytime drowsiness. But there aren’t enough large, long-term studies to say with certainty that it’s safe.”
(Steven Holfinger, MD, a sleep medicine physician at The Ohio State University Wexner Medical Center in Columbus.)
The long-term safety profile of melatonin is still being studied. However, a 2022 systematic review published in Sleep Medicine Reviews found that long-term use (up to 12 months) in both children and adults did not show serious adverse effects. That said, the authors also emphasised the need for more high-quality research.
There are concerns that long-term, nightly use of melatonin might:
Suppress natural melatonin production
Disrupt hormonal development (especially in children)
Interfere with reproductive hormones
Lead to dependency or psychological reliance
Although melatonin is not considered addictive, the idea of 'needing' a pill to fall asleep can lead to behavioural dependence.
More recently, concerns about long-term safety have been raised by a large observational study presented at the American Heart Association Scientific Sessions 2025. Reviewing health records from over 130,000 adults with chronic insomnia, researchers found that individuals using melatonin for a year or longer were more likely to be diagnosed with heart failure, be hospitalised for the condition, or die from any cause compared with matched non-users. Long-term users showed around a 90 percent higher risk of new heart failure over five years, alongside higher rates of hospitalisation and all-cause mortality.
The findings are preliminary, based on a non-peer-reviewed research abstract, and do not prove causation, but they highlight important gaps in long-term cardiovascular safety data and underline the need for caution with prolonged, nightly melatonin use.
How Much Melatonin Is Too Much?
Melatonin dosage can vary wildly across products and countries. In the UK, prescribed doses typically range from 2 mg (prolonged release) to 5 mg, taken one hour before bed.
In contrast, many American supplements contain 10 mg or more — well above what most experts recommend.
Research from the Journal of Clinical Sleep Medicine shows that lower doses (0.5 to 3 mg) are often just as effective and carry fewer side effects. Taking more does not necessarily mean better sleep and could backfire by causing daytime drowsiness or hormonal disruption.
Should Melatonin Be Used as a Long-Term Solution?
Melatonin is best used as a short-term aid or for specific sleep conditions like delayed sleep phase disorder or shift work disorder. The NHS does not recommend indefinite use. Instead, it’s most effective when combined with behavioural strategies, such as:
Maintaining a consistent sleep schedule
Reducing screen exposure before bed
Managing caffeine and alcohol intake
For those with chronic insomnia, cognitive behavioural therapy for insomnia (CBT-I) is the gold standard treatment, as recommended by NICE.
According to, Dr. Ana Krieger, medical director of the Center for Sleep Medicine at Weill Cornell Medicine and NewYork-Presbyterian:
"Relying on melatonin supplements alone without optimizing your nighttime habits, is often not the best approach."
When Might Long-Term Melatonin Use Be Justified?
There are specific medical contexts in which longer-term melatonin use may be considered appropriate when prescribed and monitored by a clinician. These include adults with neurodegenerative conditions such as Alzheimer’s disease, children with neurodevelopmental disorders who experience persistent sleep difficulties, and individuals with non-24-hour sleep-wake disorder, a condition most commonly seen in people who are blind.
Even in these situations, ongoing supervision is essential, with regular review of effectiveness, dosage, and potential side effects to ensure continued benefit and safety.
Natural Alternatives to Melatonin
For those seeking a non-hormonal sleep aid, the following options may offer support:
Magnesium: Promotes relaxation and reduces cortisol levels.
Valerian root: A herbal remedy with sedative effects, commonly used in the UK.
Glycine: An amino acid shown to lower core body temperature and support sleep onset.
L-theanine: An amino acid from green tea that promotes relaxation without sedation.
These alternatives can often be taken long-term with fewer risks than melatonin, but they still benefit from a conversation with a healthcare provider.
Melatonin vs. Other Sleep Aids: A Safety Comparison
Sleep Aid | Type | Available in UK OTC? | Safe for Nightly Use? |
Melatonin | Hormone | No | Possibly, with medical advice |
Magnesium | Mineral supplement | Yes | Yes (generally safe) |
Valerian Root | Herbal remedy | Yes | Likely safe, but can cause drowsiness |
Diphenhydramine | Antihistamine | Yes | Not recommended long-term |
Glycine | Amino acid | Yes | Yes |
L-theanine | Amino acid | Yes | Yes |
Melatonin is often seen as more 'natural' than prescription sleeping tablets, but it's still a hormone, meaning it affects the body's endocrine system. For that reason, regular long-term use without guidance is not advisable.
Final Verdict: Is It Safe to Take Melatonin Every Night?
In the UK, melatonin is a prescription-only medication for a reason: it can be safe when used correctly, but it is not risk-free. Occasional or short-term use under medical supervision is generally well-tolerated. However, nightly, long-term use should be approached cautiously.
Those struggling with persistent insomnia or circadian rhythm issues should speak to a GP or sleep specialist. Alternatives like magnesium, glycine, or CBT-I may offer more sustainable results.
Frequently Asked Questions
Can I get melatonin online in the UK?
Only through licensed online pharmacies with a prescription. Be wary of unregulated imports.
Is melatonin addictive?
No, but psychological dependence is possible.
Can children take melatonin?
Only under medical supervision for specific conditions.
What’s the best time to take melatonin?
Yes, this is one of the most evidence-backed uses of melatonin.
Is it OK to take melatonin for jet lag?
For more science-backed guidance on sleep supplements, see our hub on vitamins for sleep.
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