melatonin at a glance
Medicine class
Melatonin receptor agonist and naturally occurring hormone.
Availability
Prescription-only medicine in the UK.
Formulations
Immediate-release and prolonged-release tablets, capsules and oral liquid; administration instructions differ.
Driving
Do not drive, cycle or operate machinery if melatonin causes sleepiness, dizziness, blurred vision or impaired concentration.
What is melatonin used for?
UK licences differ between products. Selected products are licensed for:
Primary insomnia with poor-quality sleep in adults aged 55 or over.
Jet lag in adults.
Insomnia in children and adolescents aged 6–17 years with ADHD when sleep-hygiene measures have been insufficient.
Delayed sleep–wake phase disorder in children and adolescents aged 6–17 years and adults up to age 25 when sleep-hygiene measures have been insufficient.
Sedation under medical supervision to facilitate an EEG in children and adolescents.
How does melatonin work?
Melatonin supplements the hormone normally released after darkness. Activity at MT1 and MT2 receptors helps align the circadian clock with the light–dark cycle and increases the tendency to sleep.
melatonin preparations and strengths
Capsule
Route: Oral
Strengths: 2 mg, 3 mg, 5 mg
Modified-release tablet
Route: Oral
Strengths: 1 mg, 2 mg, 5 mg
How to take melatonin
Follow the instructions for the exact prescribed product because food and formulation affect absorption.
Swallow prolonged-release tablets whole; crushing or chewing can destroy their release characteristics.
Mellozzan immediate-release tablets may be crushed and mixed with water immediately before administration.
Swallow hard capsules whole with fluid.
Measure oral solution with the supplied oral syringe or measuring device.
Food instructions differ: prolonged-release products are taken after food, whereas some immediate-release products should be separated from meals.
Avoid alcohol and do not drive or operate machinery if impaired.
melatonin side effects
Common or expected effects
- Daytime sleepiness or tiredness
- Headache
- Dizziness
- Nausea or abdominal discomfort
- Irritability or restlessness
- Dry mouth
- Unusual dreams or night sweats
Get urgent medical advice
- Signs of anaphylaxis, including facial or throat swelling and breathing difficulty
- Fainting or loss of consciousness
- Severe chest pain
- Unexplained bleeding, bruising or blood in the urine
- Marked confusion, vertigo or visual disturbance
melatonin in pregnancy
Melatonin is not usually recommended during pregnancy because human safety information is limited and it crosses the placenta. Ask the prescriber to review treatment if pregnant, planning pregnancy or pregnancy occurs during treatment.
melatonin while breastfeeding
Product information commonly advises against breastfeeding, while NHS and SPS guidance says cautious use may sometimes be possible after professional assessment when the baby is healthy. Monitor for unusual sleepiness, poor waking for feeds or feeding difficulty, and do not share a bed with the baby while taking melatonin.
melatonin interactions
Ask a pharmacist or prescriber to check medicines and supplements because melatonin is affected by CYP1A enzymes and can add to sedation.
Fluvoxamine
Can greatly increase melatonin exposure; selected product information advises avoiding the combination.
Benzodiazepines, opioid analgesics and other sedatives
May increase drowsiness and impair alertness.
Oestrogen-containing contraception or HRT
May increase melatonin concentrations and adverse effects.
Common questions about melatonin
Answers are fully visible for fast scanning and source review.
Is melatonin available without a prescription in the UK?
No. It is a prescription-only medicine in the UK.
Can children be prescribed melatonin?
Yes, but selected products are licensed only for defined paediatric conditions, and specialist assessment is generally required. Products should not be substituted automatically.
More questions about melatonin
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.