Can Nyquil Make You Sleepy?

There are many Nyquil products to choose from, most of which can cause sleepiness. In general, you’ll start to feel drowsy within a half an hour of taking Nyquil.

Nyquil products may contain several or all of the active ingredients listed below at varying doses. Nyquil Severe products tend to contain additional ingredients.

Acetaminophen

Acetaminophen is a common pain reliever. It targets symptoms such as minor aches and pains, fever, headache, and sore throat. It carries a low risk of side effects when taken at the recommended dosage.

However, higher doses of acetaminophen can be dangerous. If you take more acetaminophen than is safe for you, it can cause liver damage. The recommended maximum daily dose of acetaminophen is 3,000 milligrams (mg). But the difference between a safe dose and a dose that could harm your liver is very small.

Acetaminophen is sold under many brand names, including Tylenol. It’s found in the following Nyquil products:

• Nyquil Cold and Flu Nighttime Relief (Liquid and LiquiCaps)
• Nyquil Severe Cough, Cold, and Flu Nighttime Relief (Liquids, LiquiCaps, and VapoCool Caplets)
• Nyquil High Blood Pressure Cold and Flu Medicine

Dextromethorphan HBr

Dextromethorphan is a cough suppressant. It works by reducing brain signals that trigger coughing.

Although side effects are typically mild, they can include:

• drowsiness
• lightheadedness
• restlessness
• gastrointestinal symptoms

Dextromethorphan HBr is found in the following Nyquil products:

• Nyquil Cold and Flu Nighttime Relief (Liquid and LiquiCaps)
• Nyquil Severe Cough, Cold, and Flu Nighttime Relief (Liquids, LiquiCaps, and VapoCool Caplets)
• Nyquil Cough DM and Congestion Medicine (Liquid)
• Nyquil High Blood Pressure Cold and Flu Medicine (Liquid)

Doxylamine succinate

Doxylamine succinate is an antihistamine. Antihistamines work by blocking the action of histamine, a substance associated with allergy symptoms.

By targeting histamine, doxylamine succinate helps relieve sneezing, runny nose, and sinus congestion. It causes significant drowsiness, as well as headaches and sinus dryness.

Doxylamine succinate is found in the following Nyquil products:

• Nyquil Cold and Flu Nighttime Relief (Liquid and LiquiCaps)
• Nyquil Severe Cough, Cold, and Flu Nighttime Relief (Liquids, LiquiCaps, and VapoCool Caplets)
• Nyquil Cough DM and Congestion Medicine (Liquid)
• Nyquil High Blood Pressure Cold and Flu Medicine (Liquid)

Phenylephrine HCl

Phenylephrine HCl is a decongestant. It relieves symptoms associated with sinus congestion, such as a runny nose. It doesn’t cause sleepiness. Other side effects include dizziness, headache, and upset stomach.

Phenylephrine HCl is found in the following Nyquil products:

• Nyquil Severe Cough, Cold, and Flu Nighttime Relief (Liquids, LiquiCaps, and VapoCool Caplets)
• Nyquil Cough DM and Congestion Medicine

There are no studies examining the safety and effectiveness of Nyquil as a sleep aid.

Some studies have examined the use of antihistamines to help with sleep. According to a 2012 literature review, some first-generation antihistamines may be helpful in treating short-term insomnia.

However, there’s relatively little research on doxylamine succinate, the antihistamine that causes drowsiness in Nyquil. The authors of a 2015 literature review concluded that there weren’t enough quality studies to determine its safety or effectiveness as a sleep aid.

In addition, doxylamine may cause undesirable side effects, including daytime drowsiness. Other side effects can include:

• blurred vision
• headache
• mouth, nose, and throat dryness
• nausea
• respiratory congestion
• restlessness

You can develop tolerance to doxylamine quite quickly, which means that if you take it regularly, its sedative effects won’t be as strong.

Given that Nyquil contains additional ingredients that can cause side effects, it’s safer to use a less risky nonprescription sleep aid for temporary relief from insomnia.

To take Nyquil safely, follow the instructions on the label. You should always speak with your doctor before taking Nyquil if you:

• have a medical condition
• are over the age of 75
• are pregnant or breastfeeding

Since Nyquil causes drowsiness, you shouldn’t combine it with other sleep aids, like melatonin for instance. This could cause potentially risky sedative effects, such as shallow breathing.

You should also avoid alcohol when taking Nyquil, as it can increase sleepiness, dizziness, and other side effects. In addition, since Nyquil contains acetaminophen, taking it repeatedly with alcohol can put you at risk of liver damage.

You shouldn’t take Nyquil with other drugs that contain acetaminophen, or you risk exceeding the recommended daily dosage.

Lifestyle changes have been shown to help with falling asleep and staying asleep. If you have a hard time getting good quality sleep, try the following:

• Stick to a sleep schedule. Going to bed at the same time each night and waking up at the same time each morning can help prevent disrupted sleep.
• Find ways to relax before bed. Adopt a routine to wind down before bed. Take a warm bath, read a book, meditate, or listen to soothing music.
• Avoid naps during the day. Don’t nap for more than 20 to 30 minutes during the day, as this may make it harder to sleep at night.
• Prepare your bedroom. Your bedroom should be used for sleep and sex only. Make sure it’s dark, quiet, and cool. Try to keep the temperature of your bedroom between 60 and 67°F (15.6 and 19.4°C).
• Avoid electronic devices. Avoid using your phone, tablet, or computer within an hour of going to bed. These devices may stimulate your brain and make it harder for you to fall asleep.
• Get regular exercise. Physical activity can help you feel tired at night. If you do moderate-intensity exercise, try to finish exercising within an hour of going to bed. More vigorous exercise should be done earlier in the day.
• Avoid substances known to disrupt sleep. Heavy meals, caffeine, and alcohol before bed can make it more difficult to fall or stay asleep.
• Reduce stress. Stress can keep you up at night. Try relaxation techniques like breathing exercises, meditation, yoga, and progressive muscle relaxation to counter stress at bedtime.
• Use an insomnia app. Smartphone apps, such as the U.S. Department of Veterans Affairs Insomnia Coach app and other insomnia apps, can help you track your sleep.

Most people experience difficulty sleeping from time to time. Talk with your doctor or healthcare provider if your inability to sleep lasts for more than a few weeks or if daytime drowsiness starts to interfere with your responsibilities at work or home.

Nyquil contains the active ingredients acetaminophen, dextromethorphan HBr, doxylamine succinate, and sometimes, phenylephrine HCl. Doxylamine is the main ingredient that causes sleepiness.

There’s no evidence to support using Nyquil as a sleep aid. If you’re having difficulty sleeping, try to make changes to your bedtime routine, stick to a regular sleep schedule, or talk with your healthcare provider about sleep aids that may help you get the restful sleep you need.