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Key takeaways
NyQuil typically lasts up to eight hours and begins working around 30 minutes after administration.
NyQuil is not meant for long-term use and should not be used for longer than a week.
When you’re dealing with a nasty virus, one of the most popular over-the-counter medication options is Vicks NyQuil. NyQuil can treat a variety of cold symptoms, such as sore throat, runny nose, coughing, sneezing, and flu symptoms like body aches or fever. Another bonus is that NyQuil can cause drowsiness, which can help you more easily sleep throughout the night rather than tossing and turning until the wee hours. Plus, it is long-lasting—providing symptom relief for six hours. However, some side effects may last for up to eight.
How long does NyQuil last?
“NyQuil can relieve symptoms for up to six hours, but the drowsiness caused by NyQuil can last up to eight hours,” says Lindsey Hudson, APRN, NP-C, certified diabetes care and education specialist working in Charleston, South Carolina, and member of the SingleCare Medical Board.
NyQuil is available as a liquid or liquigel. It contains the following active ingredients:
- Acetaminophen, sold under the brand name Tylenol, is a pain reliever and fever reducer.
- Dextromethorphan HBR, which is the generic form of Robitussin, is a cough suppressant.
- Doxylamine succinate is an antihistamine—a medicine that relieves symptoms of allergies and hay fever—that has sedative effects.
Depending on the person, the symptom relief provided by the acetaminophen and dextromethorphan in NyQuil can last from four to six hours, but doxylamine succinate can continue working for up to eight hours. This means while some of NyQuil’s benefits wear off at up to six hours, it may take NyQuil eight hours to wear off fully.
How long does NyQuil take to work?
While NyQuil may last up to eight hours, it doesn’t immediately begin working when you take it. “In general, NyQuil takes up to 30 minutes to begin working after administration,” says Hudson. “Depending on the dosage and your metabolism, some people may even feel the effects within 15 minutes.”
NyQuil can be taken with or without food. Sometimes, NyQuil may cause stomach irritation. For those who are more sensitive to medications, taking food with NyQuil can help prevent an upset stomach.
Adequate sleep is always important, but it is even more so when your body is fighting off a cold, cough, flu, or other sickness. NyQuil is designed to make people tired so they can sleep better when they feel unwell. That means when using NyQuil, you shouldn’t plan on doing anything that requires you to be awake and alert for up to eight hours after each dose. Because of this side effect, many people prefer to take NyQuil about 30 minutes before going to bed so the medication has time to start working and make you feel sleepy.
NyQuil side effects
The most common side effect of NyQuil is feeling tired or groggy the next morning after taking it. This is common due to the antihistamine it contains. Additionally, there are other side effects, including:
- Sleepiness
- Dizziness
- Upset stomach or nausea
- Dry mouth or eyes
- High blood pressure
Rare but serious side effects may include:
- Shaking or tremors
- Mood changes
- Rash
- Seizure
“Children younger than 12 shouldn’t take NyQuil, and anyone with high blood pressure should not use NyQuil excessively,“ said Marilyn Mercedes, Pharm.D., Associate Director of Pharmacy Operations with SBH Health System in Washingtonville, New York. Nyquil should also be avoided by older adults because it can increase the risk of certain side effects.
There are a few other considerations when taking this cold medicine. NyQuil should not be taken with alcohol since it contains acetaminophen, and mixing acetaminophen and alcohol could cause liver damage over time. Alcohol can also increase certain side effects, like dizziness and drowsiness. NyQuil should also be avoided by those who are breastfeeding.
How long should you take NyQuil?
NyQuil is intended only for short-term use. “NyQuil should not be taken long-term as the ingredients in it can cause side effects if abused,” says Dr. Mercedes. “NyQuil has dextromethorphan, which should only be consumed for less than two weeks.”
If symptoms persist longer than two weeks, you should visit a healthcare provider for medical advice to ensure there are no serious underlying medical issues.
You should stop taking NyQuil if you experience negative side effects or have taken it more than seven nights in a row. It is not intended to be used as a sleep aid, as it is possible to become addicted to NyQuil.
There are several different versions and formulations, so make sure to read the instructions on the packaging to ensure you are taking the proper dose of NyQuil. For example, the dosing instructions for NyQuil Cough, Cold & Flu Nighttime Relief LiquiCaps are 2 LiquiCaps with water every 4 hours for adults, while the NyQuil Cold & Flu Nighttime Relief Liquid dosage is measured with the provided measuring cap.
NyQuil alternatives
If NyQuil isn’t right for you, there are other over-the-counter (OTC) options to treat cold and flu symptoms. Typically, a more affordable option is the drugstore’s generic brand, which is sold under a different name but includes the same ingredients.
For daytime relief, try Dayquil. Instead of the antihistamine that causes drowsiness, Dayquil contains phenylephrine, a nasal decongestant. However, recent FDA data suggests this ingredient is not effective.
Consider your symptoms when looking for alternatives to NyQuil. If your main symptom is coughing, cough syrups like Robitussin or Delsym could work. If you have a fever and body aches, pain relievers like Tylenol, Aspirin, Advil, or Excedrin can be helpful.
Speak with your healthcare provider or pharmacist to make sure Nyquil or other OTC medications are a safe option for you.
Sources
- Find answers to frequently asked questions, Vicks FAQ (2024)
- FDA clarifies results of recent advisory committee meeting on oral phenylephrine, U.S. Food and Drug Administration (2023)