Can Melatonin Cause Vomiting? A Guide to Side Effects and Safe Use

October 12, 2025 •

4 min read

In the United States, melatonin use among adults increased from 0.4% in 1999–2000 to 2.1% in 2017–2018 [1.6.2]. As its popularity grows, many users ask: Can melatonin cause vomiting? While generally safe, this supplement is associated with certain side effects worth understanding.

Quick Summary

Melatonin can cause gastrointestinal side effects, including nausea and, more rarely, vomiting [1.2.1, 1.2.3]. This reaction is often linked to high doses, individual sensitivity, or taking the supplement on an empty stomach [1.8.1].

Key Points

Direct Link: Yes, melatonin can cause vomiting, though it is considered an uncommon side effect, more often associated with high doses or overdose [1.2.1, 1.2.2].
Nausea is More Common: Users are more likely to experience nausea, stomach cramps, and other gastrointestinal issues than actual vomiting [1.3.2, 1.3.4].
Dosage is Critical: The risk of side effects like vomiting increases significantly when taking more than the recommended dose (typically 1-5 mg) [1.2.3].
Overdose Symptom: Vomiting, along with excessive sleepiness and breathing trouble, is a key sign of melatonin overdose, especially in children [1.4.6].
Lack of Regulation: Because the FDA does not regulate melatonin supplements, the actual dose can be much higher than labeled, increasing the risk of side effects [1.7.2, 1.7.3].
Safe Use Practices: To minimize risk, start with a very low dose (0.5-1 mg), take it with food, and choose a product verified by a third party like USP [1.7.2, 1.8.2].
Consult a Doctor: Always speak with a healthcare provider before starting melatonin, especially for children or if you have existing health conditions [1.5.3, 1.8.3].

What is Melatonin?

Melatonin is a hormone your brain's pineal gland produces naturally in response to darkness [1.5.5]. It helps regulate your body's internal clock, also known as the circadian rhythm, signaling that it's time to sleep [1.5.5, 1.7.4]. Because of its role in sleep, synthetic melatonin is widely sold as an over-the-counter dietary supplement to address issues like insomnia, jet lag, and other sleep disorders [1.5.5]. However, because it's classified as a supplement in the U.S., it is not regulated by the Food and Drug Administration (FDA) in the same way as prescription drugs [1.6.1, 1.7.4].

The Lack of FDA Regulation

This lack of regulation leads to significant inconsistencies. A 2017 study found that the actual melatonin content in supplements can range from -83% to +478% of what is stated on the label [1.5.5]. Furthermore, a study of melatonin gummies found 88% were inaccurately labeled [1.6.1]. Some supplements have even been found to contain other substances, like serotonin or CBD, which are not listed on the label [1.6.1, 1.9.1]. This variability makes accurate dosing difficult and can increase the risk of side effects [1.7.2].

Can Melatonin Cause Vomiting?

Yes, melatonin can cause vomiting, although it is not one of the most common side effects [1.2.1, 1.2.3]. Nausea is reported more frequently [1.3.1]. Vomiting is more likely to occur under specific circumstances, particularly with high doses or in cases of an overdose [1.2.2, 1.4.1]. Both adults and children can experience vomiting as a symptom of taking too much melatonin [1.4.3, 1.4.4]. In fact, calls to U.S. Poison Control centers regarding melatonin ingestion in children increased by 530% between 2012 and 2021, with vomiting being a noted symptom [1.6.1, 1.7.1].

Factors That Increase the Risk of Vomiting

Several factors can increase the likelihood of experiencing nausea or vomiting after taking melatonin:

High Dosages: Experts state that nausea and vomiting are common side effects of taking too much melatonin [1.2.3]. While a standard dose is typically 1-5 mg, some people take much higher amounts, increasing their risk [1.2.3, 1.5.4].
Taking it on an Empty Stomach: Some sources recommend taking melatonin with a small snack or after food to reduce the chance of nausea and stomach ache [1.8.1, 1.8.2].
Individual Sensitivity: People react to supplements differently. Melatonin is known to be produced in the gastrointestinal tract, where it influences gut motility [1.3.1, 1.3.4]. For some individuals, supplementation can disrupt this natural balance, leading to cramps, diarrhea, or nausea [1.3.1].
Contaminants and Fillers: The presence of unlisted ingredients, such as serotonin, in unregulated supplements could contribute to adverse reactions [1.9.1]. Combining melatonin contaminated with serotonin with other serotonergic medications like antidepressants can lead to a serious condition called serotonin syndrome, which can include symptoms like nausea and vomiting [1.9.1, 1.9.4].

Comparison of Side Effects: Melatonin vs. Prescription Sleep Aids


Feature	Melatonin	Prescription Sleep Aids (e.g., Zolpidem)
Regulation Status	Dietary Supplement (not FDA regulated for purity or dose) [1.7.4]	FDA-Approved Drug (regulated) [1.5.5]
Common GI Side Effects	Nausea, stomach cramps, diarrhea, constipation [1.3.2]	Less common, but possible.
Vomiting Likelihood	Uncommon, primarily with high doses or overdose [1.2.1, 1.4.6]	Rare, but a possible side effect.
Other Common Side Effects	Drowsiness, headaches, dizziness, vivid dreams [1.2.1]	Daytime drowsiness, dizziness, impaired balance [1.5.5]
Risk of Dependency	Considered non-habit-forming for short-term use [1.8.3]	Higher potential for dependency and withdrawal.

How to Minimize the Risk of Side Effects

If you choose to take melatonin, you can take steps to reduce the risk of vomiting and other adverse effects:

Start with a Low Dose: Healthcare professionals recommend starting with the lowest effective dose, which can be between 0.5 mg and 1 mg, and gradually increasing it if necessary [1.5.4, 1.8.2]. Doses over 5-10 mg are generally not recommended without medical supervision [1.5.6].
Take It with Food: Taking your melatonin supplement with a small snack may help prevent nausea and stomach upset [1.8.1].
Choose a Verified Product: Look for supplements that have been independently tested by a third party, such as a product with a USP (United States Pharmacopeia) verified mark. This helps ensure the product contains the ingredients and dosage listed on the label [1.7.2].
Avoid Alcohol: Combining alcohol with melatonin can increase drowsiness and may worsen other side effects [1.8.1, 1.8.2].
Consult a Healthcare Provider: Before starting melatonin, it's essential to talk to your doctor, especially if you have underlying health conditions (like an autoimmune disease or diabetes), are pregnant, or take other medications [1.3.6, 1.8.3]. They can help you determine if melatonin is safe and appropriate for you.

When to See a Doctor

Stop taking melatonin and consult a doctor if you experience severe or persistent vomiting, stomach pain, or other concerning side effects [1.8.1]. If you suspect an overdose in an adult or child—with symptoms like excessive sleepiness, repeated vomiting, or trouble breathing—seek immediate medical attention [1.2.2, 1.4.6].

Conclusion

While melatonin is a popular sleep aid, it is important to be aware of its potential side effects. Vomiting is not a common reaction at standard low doses but becomes a significant risk with high doses and overdose [1.2.1, 1.2.3]. The supplement's lack of FDA regulation means product quality and dosage accuracy can vary widely, potentially contributing to adverse effects [1.7.1]. To use melatonin safely, users should start with a low dose, select a third-party verified product, and consult with a healthcare professional to minimize risks and ensure it is the right choice for their sleep concerns.

Authoritative Link: For more information on melatonin, visit the National Center for Complementary and Integrative Health (NCCIH). [1.7.5]

Frequently Asked Questions

The most common side effects of melatonin are drowsiness, headaches, and dizziness. Some people also report experiencing vivid dreams or nightmares [1.2.1, 1.3.4].

There isn't an official toxic dose, as sensitivity varies, but some healthcare professionals believe doses of 30 mg or more may be harmful. An overdose is generally defined as taking more than your body can handle, which can occur even at lower doses for some individuals [1.5.4]. Vomiting is a sign of overdose [1.4.4].

Yes, children can experience side effects from melatonin, including nausea, vomiting, stomach pain, and bedwetting [1.2.5, 1.4.2]. Vomiting is considered a sign of poisoning or overdose in children, and you should seek medical attention if it occurs [1.4.3].

The form itself doesn't inherently change the risk, but the dosage and product quality do. Gummy supplements are a particular concern for accidental overdose in children because they resemble candy [1.2.5]. Inaccurate labeling is a problem across all forms [1.7.3].

Mild side effects like nausea or daytime drowsiness are typically temporary and resolve within a few hours as the supplement clears from your body. If side effects persist, you should reduce the dose or stop taking it and consult a doctor [1.8.2, 1.8.5].

If you vomit after taking melatonin, it could be a sign you've taken too much. You should not try to induce more vomiting. Stop taking the supplement and monitor your symptoms. If vomiting is severe or accompanied by other signs of overdose like extreme drowsiness or difficulty breathing, seek medical help immediately [1.8.5].

Melatonin appears to be safe for most people for short-term use (one to two months) [1.6.1]. The long-term effects of nightly use have not been well-studied, and some experts express concern, so it's best used for occasional issues and under the guidance of a doctor for chronic use [1.5.5, 1.8.4].