Melatonin side effects commonly include which of the following?

• A. Excessive sleepiness and reduced psychomotor and neurocognitive function
• B. Increased alertness and insomnia
• C. Severe hypertension
• D. Weight gain

Answer: (A)

Melatonin helps regulate the sleep-wake cycle, so taking it can leave you feeling sleepy or groggy during the day and may slow your reaction time and thinking. This lingering sedative effect is why excessive sleepiness and reduced psychomotor and neurocognitive function are the typical side effects. The other options describe effects that aren’t commonly seen with melatonin—it doesn’t usually increase alertness or cause insomnia, and severe hypertension or weight gain aren’t typical. In practice, if you take melatonin, start with a low dose and avoid activities requiring sharp focus until you know how it affects you.