Can you overdose on melatonin?

You may be wondering if you can overdose on melatonin, a popular natural sleep aid. The term “natural” often gets misinterpreted as “risk-free,” but this is not true. Melatonin supplements are generally safe, but taking high doses can be risky, especially when combined with other substances. 

As with all medicines and dietary supplements, following the product label’s dosing instructions is important to avoid an overdose. Keep reading to learn more about melatonin, its dosage, side effects, and overdose risks. 

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Melatonin, the “sleep hormone,” is naturally produced by the pineal gland in your brain. It plays a significant role in controlling your body’s internal clock or circadian rhythm and signaling your body’s sleep-wake cycle. Melatonin production naturally rises a few hours before sleep in response to dim light (Savage, 2021; Masters, 2014).

Melatonin is available as a dietary supplement. It contains synthetic (lab-created) melatonin and is commonly used as a sleep aid for short-term sleep troubles due to jet lag, shift work, or insomnia.

While rare, it is possible to overdose on melatonin. Melatonin is a popular natural sleep aid because it’s generally safe and carries a low risk of unwanted side effects. But there are several documented cases of people who developed serious side effects after taking too much melatonin.

Most adults who have reportedly overdosed on melatonin were intentionally abusing it or taking it along with other drugs or substances. Melatonin may worsen the side effects of other sleeping pills like zolpidem (Otmani, 2008).

In one report, a 58-year-old individual was hospitalized for a serious heart problem called endocarditis after crushing and injecting 5-mg melatonin tablets. He also experienced suicidal thoughts and other symptoms, but he did recover (Warren, 2016).

In another report, a 66-year-old man became confused and lethargic (extremely drowsy) after taking 24 mg of melatonin. He also admitted that he normally took 6 mg of melatonin nightly along with sedative drugs (Holliman, 1997).

It isn’t clear if a melatonin overdose can be life-threatening, but it’s possible. Unfortunately, a death occurred in a 3-month old female infant whose parents reportedly gave her 40 mg to 50 mg of dissolvable melatonin. The parents also gave the same amount of melatonin to the infant’s twin sister, who was unharmed. It was not determined if melatonin overdose was responsible for the infant’s death (Shimomura, 2019).

In the United States, melatonin is available over-the-counter, without a prescription. It is a dietary supplement and not a drug, so it isn’t approved or regulated by the Food and Drug Administration (FDA). Because of this, there is no official recommended or maximum dosage of melatonin. According to the FDA, dietary supplements “are not intended to treat, diagnose, prevent, or cure diseases” (FDA, 2020).

There is no clearly defined limit on how much melatonin you can safely take, but it's best to follow the instructions on the product label for your melatonin supplement. Many different strengths and formulations of melatonin exist on the market, so the directions can vary.

The typical melatonin dosage ranges from 0.1 mg to 10 mg, taken up to two hours before bedtime (Savage, 2021). Most studies have shown that melatonin doses of 0.3 mg to 5 mg are generally safe and modestly effective for sleep (Ferracioli-Oda, 2013; Costello, 2014).

In the European Union, melatonin is available as a prescription drug called Circadin. Circadin contains an extended-release formulation of melatonin, and the recommended dosage is 2 mg once daily, one to two hours before bedtime. It’s approved as a short-term treatment for insomnia with poor sleep quality in older adults, ages 55 years and up (EMA, 2012).

According to a study, taking an extended-release melatonin 2 mg nightly for six months did not cause harmful side effects (Wade, 2010).

Melatonin may interact with several medications. Some interacting drugs or substances can interact with melatonin, possibly increasing the risk of overdose. Some examples include (EMA, 2012): 

• Alcohol 

• Benzodiazepines like lorazepam (Ativan) may cause excessive sleepiness when combined with melatonin. 

• When taken with melatonin, sleeping pills like zolpidem (Ambien) may cause excessive drowsiness and impaired attention, memory, and coordination.

• Medications that contain estrogens, such as birth control pills and hormone replacement therapy, can increase melatonin levels.

• Cimetidine (Tagamet) is an over-the-counter drug used to relieve heartburn. It can raise melatonin levels.

• Methoxsalen (Oxsoralen-Ultra), a psoriasis treatment, can increase the levels of melatonin.

• Quinolones antibiotics, such as levofloxacin (Levaquin), can raise melatonin levels.

• Certain antidepressants may increase the risk of side effects with melatonin. ​​Fluvoxamine (Luvox) is an antidepressant medication that has been shown to raise melatonin levels significantly. Combining melatonin with the antidepressant imipramine (Tofranil) caused feelings of confusion in a study (EMA, 2012).

• Thioridazine, an antipsychotic medication used to treat schizophrenia, made performing tasks more difficult when taken with melatonin in a study (EMA, 2012).

Other considerations when taking melatonin include (EMA, 2012):

• Cigarette smoking may reduce melatonin levels, possibly making melatonin supplements less effective.

• Carbamazepine (Tegretol) is an anticonvulsant (anti-seizure) medication used to treat epilepsy. It’s known to lower the levels of melatonin in the body. In general, people who take anti-epileptic drugs should be cautious about taking melatonin.

• Rifampin, an antibiotic used to manage tuberculosis, can potentially reduce the levels and effectiveness of melatonin.

• Some evidence suggests that melatonin may have blood-thinning effects, especially if it’s used along with anticoagulant or blood thinner medications like warfarin (Coumadin) (Ashy, 2016).

• Certain blood pressure medications, such as nifedipine, may become less effective if taken with melatonin and could increase blood pressure or heart rate (Lusardi, 2000). 

The list above does not include all possible interactions with melatonin. It’s best to consult your healthcare provider or pharmacist before taking melatonin if you’re already taking any prescription or over-the-counter medications. 

At usual doses of 0.1 mg to 10 mg per day, melatonin doesn’t usually cause serious side effects. The most common side effect is the usual intended effect: drowsiness. So, it is best not to drive after taking melatonin. Other common side effects of high doses of melatonin may include (Savage, 2021):

• Headaches

• Nausea

• Rash

• Stomach upset

• Nightmares or vivid dreams

• Daytime sleepiness that occurs the day after taking melatonin

If any of these side effects become severe, it could be a sign that you’ve taken too much melatonin.

If you think you’ve taken too much melatonin along with alcohol, other drugs, or sleep aids that cause drowsiness, you should seek immediate medical care. Poison control help is available online or by calling 1-800-222-1222.

When you’re considering how much melatonin to take, it’s best to start with a low dosage, such as 0.1 mg to 2 mg up to two hours before bedtime (Savage, 2021; Wade, 2010). 

It’s also important to set yourself up for a good night’s sleep with basic sleep hygiene habits. If you still have questions about melatonin or trouble sleeping, do not hesitate to ask a pharmacist or healthcare provider for medical advice.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

September 09, 2021

Written by

Patricia Weiser, PharmD

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.