Is it safe to mix Benadryl and melatonin to sleep?

It’s 2 a.m. and you’re lying in bed, wide awake. Despite tucking in hours ago, you have yet to fall asleep. Or, perhaps you drifted off for a few hours, but now peaceful slumber eludes you. Trouble falling asleep—or staying asleep—is a fairly common problem. Insomnia affects 10% to 30% of the adult population, according to studies, mostly impacting women, older adults, and people with medical or mental health issues. Short-term insomnia becomes chronic insomnia when symptoms last longer than three months, says Jay Guevarra, MD, a sleep medicine physician at Mount Sinai in New York City. 

Getting an inadequate amount of sleep can have numerous consequences. They range from something as small as falling asleep at your desk to more significant, long-term issues such as depression and poor quality of life. It’s no wonder, then, that many people suffering from sleepless nights reach for an over-the-counter supplement (like melatonin) or medication (like Benadryl)—or perhaps a combination of the two—to help them fall asleep. But is it safe to take melatonin and Benadryl together? And will that combination of meds really help you get better sleep?

RELATED: How much does the average person sleep?

Why do people take melatonin supplements?

Melatonin is a naturally occurring hormone produced by the brain in response to darkness.

“It helps to regulate your body’s internal clock known as your circadian rhythm,” says Kristi C. Torres, Pharm.D., a member of SingleCare’s Medical Review Board. “This internal clock is part of how your body knows to sleep during the night, dark hours, and be awake during the daylight hours.”

As we get older, our bodies produce less melatonin, which is why people often sleep less, or have worse sleep quality, as they age. But it’s a common misunderstanding that melatonin or melatonin supplements make you sleepy, says Dr. Guevarra.  

“Melatonin promotes a state of quiet wakefulness or drowsiness, then in turn, your body prepares for falling asleep,” she says. “It peaks in the middle of the night, and as daylight hours come, [melatonin] levels decrease.”

In addition to addressing insomnia, a melatonin supplement can be taken to treat symptoms of jet lag, sleep disorders in children, and circadian rhythm sleep disorders in the blind, according to the Mayo Clinic. People who do overnight shift work may also use melatonin to try to reset their 24-hour sleep-wake cycle, says Dr. Torres. 

Dr. Guevarra recommends her patients start with 1 or 2 milligrams of melatonin taken two hours before bed. She adds that if you find yourself working up to 10 milligrams a night (the maximum recommended dosage), it’s “really not as efficacious at that point.” It’s worth noting that because melatonin is a dietary supplement and not a drug, it isn’t fully regulated by the U.S. Food and Drug Administration (FDA), like prescription and OTC drugs are. A 2017 study published in the Journal of Clinical Sleep Medicine, which examined 31 different melatonin supplements, found that 71% of the supplements studied had a dosage that did not match what was listed on the label.

You shouldn’t rely on melatonin to sleep, and you should use it for as short of a period as possible. “If you are having trouble sleeping at night, the short-term use of melatonin may help,” Dr. Torres says. “If the insomnia is persistent, however, you should discuss this with your healthcare provider. There may be other issues affecting sleep.”

Common side effects of melatonin include vivid dreams (or nightmares), which could ultimately impact your sleep; grogginess or sleepiness during the next day; and headaches. The Cleveland Clinic also notes melatonin could make you dizzy and irritable. There’s also the small possibility of an allergic reaction, according to the National Institutes of Health (NIH). If you have symptoms of hives, difficulty breathing, or swelling of the face, lips, tongue, or throat, seek emergency medical help. 

Be aware that melatonin may interact with drugs such as birth control and blood pressure medicines, so check with your healthcare provider before using it. 

“It can make blood pressure medications less effective, so you should always discuss your decision to take melatonin with your doctor first,” Dr. Torres says. “Drugs that are classified as narcotics, barbiturates, or benzodiazepines could be more dangerous when taken with melatonin.”

Why does Benadryl make you sleepy? 

Benadryl (diphenhydramine) is an over-the-counter (OTC) medication used to treat hay fever and allergy symptoms such as sneezing, running nose, rash, and red, irritated eyes. People also use Benadryl as a sleep aid because of its status as an antihistamine. (Unisom, or doxylamine, is another popular brand-name antihistamine used for this purpose.) 

In addition to causing allergic reactions, “histamine is a chemical produced by the brain that promotes wakefulness, so antihistamines, like Benadryl, block its ability to bind to the right receptors in order to promote wakefulness—and that promotes sleepiness,” explains Dr. Guevarra. This side effect is why first-generation antihistamines are used for sleep. 

The general dosage guidelines for adults (those 12 and older) of Benadryl is one to two 25 to 50 mg capsules 30 minutes before bedtime. If you’re using a liquid formulation, read the dosage instructions and carefully measure the dose with a medication-measuring device. 

The most common side effects of Benadryl are drowsiness and dizziness. (Taking another medication that causes these effects in conjunction with Benadryl—including opioid pain medicine, a benzodiazepine for anxiety, or even certain cough syrups—will compound the sleepiness effect, says Dr. Torres.) You may also experience a dry mouth or nose, lack of appetite, and constipation. 

In addition to being an antihistamine, Benadryl is an anticholinergic—meaning it blocks the neurotransmitter acetylcholine, which plays a role in memory. Long-term use of anticholinergics has been linked with an increased risk of dementia, according to research.     

“That [risk] led to this movement, especially in the sleep field, to discourage patients from taking Benadryl chronically as a sleep aid,” says Dr. Guevarra.  

Can you take Benadryl and melatonin together?

Although there are no specific drug interactions linked to mixing Benadryl and melatonin, medical professionals generally frown on taking the two together. The combination can cause excess sedative effects and daytime sleepiness, which makes activities like driving a car or operating other heavy machinery dangerous. 

“You should not take two drugs that cause sedation without first speaking to your healthcare provider,” Dr. Torres advises. “You will want to discuss all risks with your healthcare team.”

If you find yourself reaching for multiple sleeping pills over the course of a few nights in a row, Dr. Guevarra says there may be an underlying medical concern causing your insomnia. 

“Conditions that can cause sleepiness include hypothyroidism and iron deficiency,” she says. “There are also actual sleep disorders that can contribute to insomnia, like sleep apnea and restless leg syndrome.” 

Either way, you’ll want to consult with your healthcare provider for medical advice—he or she may have you undergo a sleep study to identify the root of your sleeplessness. 

Ways to sleep better without sleep aids

Oftentimes, the best way to ensure a good night’s rest is to stick to a proper sleep and nighttime routine. One of the easiest—and most crucial—sleep habits to follow is going to bed and waking up at the same time every day, including weekends.

“When you have different schedules on weekends and days off, that throws your body off-kilter,” Dr. Guevarra says. Establish a regular bedtime and wake-up time that allows you to get the right amount of sleep for you. While that number varies, the average recommendation is seven to eight hours of sleep per night. 

What you do before you get into bed is also important. You should stop drinking caffeinated beverages at least six hours before you plan to go to sleep. Put down your blue light-emitting devices (such as phones) at least two hours before bed, so as not to negatively impact the body’s melatonin production. If you need to look at your phone before you sleep, wear glasses that block blue light. Dr. Guevarra also recommends not scrolling social media or watching TV shows that might hype you up right before bed. Instead, engage in soothing activities like taking a warm bath, reading a relaxing book, or meditating. 

Before you get into bed, set the thermostat between 60 and 70 degrees as most people tend to sleep better in a cooler room. Also, try to limit disturbances that could wake you up in the middle of the night, such as a pinging phone or a restless dog at the foot of your bed. 

By establishing good sleep hygiene, you may be able to resolve some of your sleep issues without relying on over-the-counter sleep aids.