Can melatonin cause headaches or dizziness?

Among the side effects people search for most, headaches and dizziness come close to the top, and with reason. The NHS includes both in its list of common side effects of melatonin, and research reviews summarised by StatPearls and the US National Center for Complementary and Integrative Health report them regularly. This guide explains what is known, what is not, and what else might be responsible.

How common are they?

"Common" in medicine-information terms means the effect has been reported often enough to be expected in a noticeable minority of people, not that most people experience it. In many studies, headache rates among people given melatonin were broadly similar to those among people given a dummy pill, which suggests that some headaches reported during melatonin use have other causes.

That does not mean the effect is imaginary. Some people clearly notice a pattern, especially when they first start or when the amount is higher. It simply means individual experience varies a great deal.

Possible reasons

The mechanism is not well established, so any explanation is partly informed speculation. Melatonin has effects on blood vessels and helps lower core body temperature in the evening, part of the body's normal preparation for sleep. Changes in blood vessel tone are known to be involved in some headaches, and small shifts in blood pressure could contribute to light-headedness, particularly on standing up.

Dizziness may also simply reflect drowsiness. Getting up at night while melatonin is active, or feeling heavy in the morning as described in Can melatonin make you groggy the next day?, can feel like unsteadiness.

Other causes worth ruling out

• Short or broken sleep, which is itself a common headache trigger.
• Changes in caffeine intake, including caffeine withdrawal on a quieter day.
• Not drinking enough fluid, especially after alcohol.
• Other medicines, including those that lower blood pressure.
• Eye strain from long screen use in the evening.

When to get advice

Mild symptoms that fade quickly are worth mentioning to a pharmacist, particularly if you take other medicines. Some symptoms should not wait: a sudden or severe headache, a headache with confusion, weakness, fever or a stiff neck, or dizziness with fainting or chest pain need urgent medical help regardless of melatonin. The NHS also advises stopping and getting help straight away for signs of a serious allergic reaction.

Common questions

Will the headaches stop if I stop melatonin?

Where melatonin is the cause, symptoms generally ease once it is stopped. If they continue, another cause is more likely and worth discussing with a GP.

Are headaches more likely with certain forms?

There is little research comparing forms on this point. What are the different forms of melatonin? explains how release types differ.

Can melatonin cause dizziness in older adults?

Older adults may be more sensitive to drowsiness and unsteadiness, which matters for falls. Melatonin and sleep in older adults covers this.