Sanja Jelic, MD, is board-certified in sleep medicine, critical care medicine, pulmonary disease, and internal medicine.

Doxylamine is a sleep aid in products like Unisom and Nyquil that you can buy over the counter. It's also an antihistamine that's used to treat nasal congestion.

Some people take doxylamine to treat insomnia. Insomnia is a sleep disorder where you have trouble falling asleep or staying asleep.

You don't need a prescription for doxylamine as it is widely available over-the-counter (OTC). But that doesn't mean the medicine doesn't come with potential side effects. Before taking doxylamine, learn the possible risks.

This article goes over how doxylamine works, its uses, and what problems it can cause.

Doxylamine is an antihistamine , a type of medication used to treat allergies. It can also reduce nighttime cold symptoms. One of its side effects is drowsiness.

Because of this effect, doxylamine is often used in over-the-counter sleep aids for those who have trouble getting to sleep or staying asleep. But note that it shouldn't be used for more than two weeks to treat insomnia.

Like many sleeping pills, doxylamine affects neurotransmitters . These are chemical messengers that send signals between brain and nerve cells (neurons). Doxylamine blocks receptors that let the chemical histamine stimulate neurons. This causes you to get sleepy.

Doxylamine works centrally (within the central nervous system) and elsewhere in the body to sedate you.

Since doxylamine is an OTC medication, risks might be slightly lower than with prescription medications that need careful monitoring. No routine tests are recommended with its use.

Ultimately, doxylamine is not the best option if you are considering taking sleeping pills. There are other choices that are better for aiding sleep.

Doxylamine doesn't promote sleep in the same way as prescription sleep medications, such as benzodiazepine and non-benzodiazepine medications.

To take a medication for its side effect—in this case, sleepiness—is not recommended.

Doxylamine is a non-habit forming medication. However, you can develop a tolerance to it, which means you'll have to take more of it over time to get the same effect. This can lead to an increased risk of other side effects.

As is the case with any medication, it's important to only use the recommended dosage for doxylamine. Doxylamine pills can typically be found in strengths of 12.5 and 25 milligrams (mg).

When used as a sleep aid, the recommended dosage for doxylamine is 25 mg, once daily, taken orally (by mouth) up to 30 minutes before bedtime. But if taking 25 mg of doxylamine makes you feel excessively drowsy the next day, you may want to reduce your dosage to 12.5 mg.

Most people begin to feel drowsy within 30 minutes of taking a 25 mg formulation of doxylamine. The sedative effects of doxylamine typically last up to six hours.

Certain groups of people shouldn't take doxylamine.

Children under 12 years of age shouldn't use doxylamine 25 milligrams (mg). Children under 6 and elderly people shouldn't use it without a healthcare provider's advice.

According to the National Institutes of Health, taking small, occasional doses while nursing shouldn't cause problems for the baby. However, larger doses or long-term use may cause drowsiness, irritability, and colicky symptoms in breastfed babies. It may also lower your milk supply.

People with many conditions should be cautious about doxylamine as it may cause problems or drug interactions. These conditions include:

If you're concerned about whether you may have problems using doxylamine, you should first consult with your healthcare provider.

Negative drug interactions are also a risk, especially with other medications that affect the brain, so be sure to review your medications with your healthcare provider or pharmacist before starting to use doxylamine.

The list of potential side effects for any drug can be quite long, and doxylamine is no exception. Although you likely wouldn't experience most side effects, and may not have any at all, some that occur commonly with doxylamine include:

While they're rare, serious side effects can result from the use of doxylamine, including:

Get our printable guide for your next healthcare provider's appointment to help you ask the right questions.

Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life.

Thank you, {{form.email}}, for signing up.

There was an error. Please try again.

Doxylamine is an antihistamine drug that is often used in over-the-counter medications to promote sleep.

Side effects can range from dizziness and headaches to confusion and serious allergic reactions. People with certain medical conditions like glaucoma and heart disease should not take doxylamine. If you want to try it to help with insomnia, talk to your healthcare provider first.

If you experience any difficulties when taking doxylamine, you should be in close contact with your primary healthcare provider. If you wish to pursue other preferred treatments for insomnia, you should likewise make an appointment and discuss the better prescription options that are available.

Effective treatment may include medications, learning better sleep habits, or cognitive behavioral therapy for insomnia (CBTI).

No. Unisom is intended as a temporary sleep aid and should not be taken for more than two weeks. If you need ongoing help falling asleep, speak to your healthcare provider. 

Yes. The doxylamine succinate in Unisom taken with vitamin B6 can treat morning sickness during pregnancy. Talk to your healthcare provider before taking the combination to be sure it’s right for you.

Doxylamine may increase the risk for dementia. This is due to its anticholinergic properties, which means it blocks neurotransmitters that transmit messages along the nervous system. According to researchers, anticholinergic medications are associated with cognitive decline.

Doxylamine promotes relaxation to ease you into sleep, but it should not be used as a regular anxiety medication. If you are experiencing anxiety, your healthcare provider can recommend an anxiety medication that is more suitable for you.

Krystal AD, Richelson E, Roth T. Review of the histamine system and the clinical effects of Hi antagonists: basis for a noew model for understanding the effects of insomnia medications. Sleep Med Rev. 2013;17(4):263-272. doi:10.1016/j.smrv.2012.08.001

Videla S, Cebrecos J, Lahjou M. Pharmacokinetic dose proportionality between two strengths (12.5 mg and 25 mg) of doxylamine hydrogen succinate film-coated tablets in fasting state: A singe-dose, randomized, two-period crossover study in healthy volunteers. Drugs R D. 2013 Jun;13(2):129-135. doi:10.1007/s40268-013-0015-7

National Library of Medicine (US). Drugs and Lactation Database. Doxylamine.

Koren G, Clark S, Hankins GDV, et al. Maternal safety of the delayed-release doxylamine and pyridoxine combination for nausea and vomiting of pregnancy; a randomized placebo controlled trial. BMC Pregnancy and Childbirth. 2015;15(1):59.

Coupland CAC, Hill T, Dening T, Morriss R, Moore M, Hippisley-Cox J. Anticholinergic drug exposure and the risk of dementia: a nested case-control study. JAMA Intern Med. 2019;179(8):1084. doi:10.1001/jamainternmed.2019.0677

By Brandon Peters, MD Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist. 

Thank you, {{form.email}}, for signing up.

There was an error. Please try again.