There are over 300 possible drug interactions with melatonin including with alcohol or other medicines that can cause drowsiness or dizziness. When used with a blood thinner like warfarin, it may increase the risk of bleeding.
Melatonin is a natural hormone that helps to regulate the sleep-wake cycle. For some people, melatonin supplements may be helpful for insomnia (trouble sleeping), jet lag and shift work sleep disorder.
In the U.S., Melatonin comes over-the-counter in various forms you take by mouth, such as tablets, liquid drops, soft gels or gummies and does not require a prescription.
Drug interactions
Sedation
Melatonin causes drowsiness and its use should be avoided or used with caution with alcohol and other sedating medicines that cause sleepiness, including:
- benzodiazepines sedatives and hypnotics
- sedating antihistamines, like diphenhydramine (Benadryl)
- opioid analgesics used for pain
- muscle relaxers
- other herbs that can also lead to drowsiness such as 5-HTP, kava, and St. John’s Wort.
Some people, especially the elderly, may also experience impairment in thinking, judgment, and motor coordination.
Risk of bleeding
As with many herbal products, blood clotting may be affected with use of melatonin with anticoagulants such as warfarin. This interaction may increase the risk of bleeding. Check with your doctor before you combine melatonin with warfarin or other blood thinners.
Seek immediate medical attention if you experience any signs and symptoms of bleeding such as:
- unusual bleeding or bruising
- dizziness or lightheadedness
- red or black, tarry stools
- coughing up or vomiting fresh or dried blood that looks like coffee grounds
- severe headache
- weakness.
Review: Drug interactions with melatonin (in more detail)
This is not a complete list of drug interactions with melatonin and is not all information you need to know for safe and effective use. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider. This information does not take the place of your doctor’s directions.