Medicines & Supplements A to Z > Melatonin


Last updated on 19/03/2021.

Overview   |   Dosage   |    Side Effects   |   Precautions  |   Tips  |   Where To Buy  

GENERIC NAME: Melatonin 


BRAND NAME(S) IN HONG KONG: Adrien Gagnon Melatonin, Circadin prolonged-release, Doctor’s Choice Sleep Support (Melatonin), Nature’s Bounty

DRUG CLASS: Hormone 

USED FOR: Insomnia, jet lag  


AVAILABLE DOSAGE FORMS: 3mg, 5mg, 10mg (tablets)

What is Melatonin for?

Melatonin is a natural hormone made by your body and responsible for regulating the sleep-wake cycle. During the night-time, Melatonin in the blood rises sharply which helps inducing sleep. It is therefore commonly used for treating insomnia or jet lag. Melatonin level declines with age and thus greater benefit is observed in elderly. Noted that Melatonin is typically taken for short-term use. Since Melatonin is a natural hormone, you are unlikely to become dependent on Melatonin or have a diminished response after repeated use.

How to use it?

Melatonin can be taken orally as tablets or capsules. If you are taking it for insomnia, you can start with 1 mg or 3 mg once daily first. If it does not work, you can increase up to 10 mg once daily. You should take it 1-2 hours before sleep to have the maximum benefit. If you are taking it for jet lag, you may take 1.5 to 3 mg orally at 11pm (local time in the destination country) on day 1, 10:30pm on day 2, and 10pm on day 3. Prolonged or extended release Melatonin products should not be crushed.

What are the side effects of Melatonin

Melatonin is safe and you are unlikely to experience side effects. However, joint pain, headache, and drowsiness may occasionally occur.

Who should not take Melatonin?

Anyone with an allergy to Melatonin or any components of the formulation.

Pharmacist Tips:

– Avoid drinking alcohol while you are taking Melatonin.
– Do not take Melatonin for more than 4 weeks unless directed by your doctor or pharmacist.
– Do not chew or crush Melatonin tablets, especially the prolonged-release preparations. Swallow whole with water.

Common dosing schedule:
You can take Melatonin with or without food.

This schedule is for reference only, adjustments may be made according to individual needs.

Some common medications Melatonin may interact with:
– Antidepressants, e.g. Fluvoxamine, Venlafaxine
– Rifampicin
Zolpidem or Zopiclone

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Melatonin in Hong Kong?

In Hong Kong, Melatonin can be an over-the-counter medicine or a prescription only medicine depending on the brands. Circadin prolonged-release Melatonin is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. Other brands of Melatonin are over-the-counter medicines and can be purchased without a prescription from any retail outlet in Hong Kong. This includes grocery stores, convenience stores, medicine shops, and pharmacies. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.

For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at

Need more information?

For detailed information about the use of Melatonin in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.