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How long does it take for NyQuil to kick in?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Feb 11, 2022.

Official answer


You should feel the effects of NyQuil about 30 minutes after you take it. In addition to relieving cold and flu symptoms, NyQuil can cause marked drowsiness, so do not drive or operate machinery until its effects have worn off.

NyQuil is used to provide temporary relief of cold and flu symptoms like sneezing, runny nose, cough, sore throat, headache and body aches. It can cause marked drowsiness, but this may help you to rest easier. Your response to NyQuil may vary from how it affects other people.

There are many different types of NyQuil products on the pharmacy shelves and it may be confusing to know which one to choose. Always check with your doctor or pharmacist if you are not sure. One of the most common NyQuil products is NyQuil Cold and Flu Nighttime Relief Liquid.

NyQuil Cold and Flu Nighttime Relief Liquid has three active ingredients:

  • acetaminophen (a pain and fever reducer)
  • dextromethorphan (a cough suppressant)
  • doxylamine (a sedating antihistamine)

Certain NyQuil products, for example, NyQuil Severe, also contain phenylephrine, a decongestant.

NyQuil Cold and Flu Nighttime Relief Liquid also contains 10% alcohol in its formulation. Alcohol is use to help dissolve the active ingredients. Not all NyQuil products contain alcohol, so be sure to check the labels or ask your pharmacist if you need to avoid it.

Learn more: Compare NyQuil Products

How long does it take to get NyQuil out of your system?

It takes about 65 to 78 hours to get all the ingredients from NyQuil Cold and Flu Nighttime Relief Liquid out of your system.

Because NyQuil Cold and Flu Nighttime Relief Liquid contains 3 active ingredients plus 10% alcohol, the length of time it will take to get all the ingredients out of your system will depend on which drug has the longest “half life”. A half-life is the amount of time it takes for drug in your body to reduce by half. In general, it takes about 4 to 5 half-lives for a drug to be eliminated from your body.

The ingredient with the longest half life is NyQuil Cold and Flu Nighttime Relief Liquid is the cough suppressant dextromethorphan with a half-life of 13 hours. Therefore, it takes about 52 to 65 hours to get all the ingredients from this NyQuil product out of your system. Elimination of drugs from your body can vary, based on your kidney or liver function, age, weight, hydration or other factors.

Acetaminophen has a half-life of about 1.25 to 3 hours, doxylamine is 10 hours, and alcohol is 4 to 5 hours.

This is not all the information you need to know about NyQuil for safe and effective use and does not take the place of the directions on the label. Review the full product information, and discuss any questions you have with your doctor or other health care provider.


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