The short answer
The most common melatonin side effects are headache, dizziness, nausea, and daytime drowsiness. Less common ones surprise people: vivid dreams or nightmares, constipation or loose stools, stomach cramps, irritability, and short term low mood.1
Many people take far more than they need. A higher dose stays in your blood into the next morning.2 If you have side effects, a lower dose taken at the same time each night is often the first thing to try, with your doctor's advice.
"I never thought it was the melatonin"
A friend of mine was taking melatonin gummies every night before bed, 5 mg or more. They started having vivid dreams and nightmares. They also woke up foggy, had an upset stomach, and felt constipated.
They never connected any of it to melatonin. When they stopped taking the gummies, the nightmares and vivid dreams went away. When they spoke to their doctor, the doctor confirmed that these can be side effects of melatonin.
Their story is common. Most people know melatonin can make you drowsy. Far fewer know about the rest of the list.
9 melatonin side effects nobody warns you about
Morning fog, the melatonin hangover
Daytime drowsiness is one of the most common side effects.1 In adults over 50, a 3 mg dose kept melatonin high into the next day, while 0.3 mg did not.2 Read why you feel groggy after melatonin.
Vivid dreams and nightmares
Some people have intense dreams or nightmares on melatonin.1 Like my friend, many never connect them to the supplement until they stop.
Constipation
This is the one that surprises people most. Constipation is a listed side effect.1 In my experience, it seems tied to the dose, and people manage it better once they know melatonin could be the cause.
Upset stomach, cramps, or loose stools
Stomach cramps, loose stools, an upset stomach, and less appetite are all on the list.1
Headache and dizziness
Both are among the most common side effects.1 Dizziness matters most if you get up at night.
Irritability and low mood
Some people feel irritable or have short term feelings of depression.1 If low mood lasts, stop and talk to your doctor.
Bladder accidents at night
Nighttime urinary incontinence is listed as a less common side effect.1
A higher risk of falls
Melatonin can raise the risk of falls, and it can cause confusion.1 Do not drive or use machinery within 5 hours of taking it.1
A dose you did not know you were taking
In a 2023 test of 25 melatonin gummies, 22 did not match their labels. Actual amounts ranged from 74% to 347% of the label.3 You may be taking more than you think.
The biggest mistake people make
What most people get wrong is thinking a low dose will make them groggy, or will not work at all. Melatonin is a chronobiotic. It is a signal that works in the dark. It works better when you take it at a regular time, to signal your body that it is time to sleep.
It is not a sedative. People think it is, and that is a huge misconception.
When people treat melatonin like a sleeping pill, they take more to feel knocked out. That extra dose is what lingers into the morning.2 That is why I believe a lower dose that is closer to your body's natural levels matters. You never want to take more of something than your body needs.
What to do if you have side effects
- Check your dose. Many products hold 5 mg to 10 mg. Ask your doctor about a lower dose. Read how much melatonin should I take.
- Take it at the same time every night, about 30 minutes before bed, not in the middle of the night.
- Choose a product you can trust. Look for one that is tested by an outside lab.
- Take a break if you need to. In my friend's case, the dreams went away when they stopped.
- Talk to your doctor if side effects do not go away, or if you take other medicines.
Stop and call your doctor if
- You feel low, confused, or not yourself.
- You fall, or feel very dizzy when you get up.
- You have a seizure, or you take medicine for seizures.
- You take blood thinners, or medicine for blood pressure, diabetes, or your immune system. Melatonin can interact with these.1
- Side effects last after you stop taking it.
On blood pressure medicine? Read melatonin and blood pressure. Worried about memory? Read can melatonin cause dementia.
Wondering about high doses or long term use? Read how much melatonin is too much and is melatonin bad for you.
If melatonin seems to keep you up instead of helping, read can melatonin keep you awake?
Where Driffly fits
A low 1 mg dose
When I chose Driffly's formula, I started with the dose. Each strip has 1 mg of melatonin, the same amount behind the European Union's approved sleep claim,4 with valerian root, lavender, chamomile, and hibiscus to support a calm wind down.*
In a survey of 23 customers who finished 30 nights with Driffly, 21 said they woke up without grogginess.5 This was a small customer survey, not a clinical study.
- 1 mg of melatonin in each strip.
- Melts on your tongue. No water and no sugar.
- Take it 30 minutes before bed, at the same time every night.
Every order comes with a 30 night money back guarantee.
Common questions about melatonin side effects
Can melatonin make you constipated?
Yes. Constipation is a listed side effect of melatonin, though it is less common.1 If you notice it, talk to your doctor about lowering your dose or taking a break.
Does melatonin give you nightmares?
It can. Vivid dreams and nightmares are a less common side effect.1 For some people, they go away when the dose is lowered or the melatonin is stopped.
Will melatonin cause weight gain?
Weight gain is not listed among melatonin's side effects by Mayo Clinic.1 Some gummies do contain sugar, so check the label.
Can melatonin cause diarrhea?
It can. Loose stools, stomach cramps, and an upset stomach are listed as less common side effects.1
What are melatonin side effects in older adults?
Older adults should watch for daytime drowsiness, dizziness, confusion, and a higher risk of falls.1 A low dose is a sensible place to start, with a doctor's advice.
Is melatonin a sedative?
No. Melatonin is a timing signal that tells your body night has started. It is not a sleeping pill. Taking more does not make it work better, and it can leave you groggy.2
Do melatonin side effects go away?
For many people, they ease when the dose is lowered or the melatonin is stopped. If they do not, see your doctor.
Sources
- Mayo Clinic. Melatonin side effects: What are the risks? Expert Answers, Adult Health.
- Zhdanova IV, Wurtman RJ, Regan MM, et al. Melatonin treatment for age-related insomnia. The Journal of Clinical Endocrinology and Metabolism. 2001;86(10):4727-4730.
- Cohen PA, Avula B, Wang YH, Katragunta K, Khan I. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA. 2023;329(16):1401-1402.
- European Commission. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods (melatonin: reduction of time taken to fall asleep, at least 1 mg per portion). 2012.
- Driffly Night 30 customer survey, 2026. 23 customers who completed 30 nights; self reported results.
Tyler Smith, RN, BSN, BA is a registered nurse and the founder of Driffly. He writes and reviews the articles in the sleep education hub. About Tyler
The author is the founder of Driffly, which sells the product mentioned in this article. This article is for education and is not medical advice. *These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.