NyQuil it takes 6 hours to stay in your body.

It is important to know how long NyQuil lasts in our systems, as it may seem like a comfortable OTC (over-the-counter) option when we are suffering from a cough, cold, allergies, or sore throat. Being an over-the-counter effective medicine, it may seem to be flawless. However, it is not so. It does have some side effects. This article is all about NyQuil: its composition, dosage, effectiveness, side effects, and most importantly, how long it stays in our bodies, so that next time you take a dose of NyQuil, you will be prepared for a NyQuil hangover the following day.

If we talk about an approximate figure of the time in which NyQuil lasts, it is around 6 hours. After consuming NyQuil, it takes 6 hours to stay in your body. Don’t ever take NyQuil in a shorter period of time than 6 hours.

NyQuil contains doxylamine, which is the main ingredient in some NyQuil tablets. This lasts for around 8 hours in the human body. You may feel dizziness in this span of time because of the nature of doxylamine.

If we include medical science here, then the half-life span of doxylamine is 10 hours. It means it can stay and dissolve in your body in around 20 hours. All of these scenarios make the time frame for Nyquil a little complicated.

What Is NyQuil?

NyQuil is a medicine from the reputed brand Procter & Gamble, widely used to get relief from the symptoms of the cold and flu. Symptoms of the cold and flu include a runny nose, sneezing, cough, sore throat, headache, body aches, etc. This is an OTC medicine available in both liquid and pill form; the liquid version is, however, more popular.

Ingredients in NyQuil

Active ingredients in Nyquil are

  1. Acetaminophen
  2. Dextromethorphan, and 
  3. Doxylamine Succinate.
  4. Sodium citrate
  5. Citric acid
  6. Propylene glycol
  7. Polyethylene glycol 

Acetaminophen is an antipyretic and a pain reliever. An antipyretic is a drug that lowers the body temperature, thereby reducing fever.

Dextromethorphan is used to suppress coughing.

Doxylamine succinate is an antihistamine that treats allergies by blocking histamines. Going by the list of ingredients in NyQuil, it becomes obvious that it provides relief from coughs, fevers, headaches, body aches, and allergies.

Citric acid has the property of acting as a flu killer, and it is present in the NyQuil in a very small amount. NyQuil is for swallowing, but citric acid works as a flu killer when it goes into the body by spraying in the nose. That’s why it exists in the NyQuil, but in a small fraction.

Polyethylene glycol and propylene glycol are used to maintain the texture of nyquil. Nyquil has the density of water and honey, and these two ingredients try to balance it. Although many experts prefer it in a spray,

When should I take NyQuil?

When you are stuck with a cold or the flu, all you want is to sleep. But sleep does not come that easily when you have a congested chest and nose, a fever, a runny nose, and a headache. This is when you lay your hands on NyQuil despite knowing that you are going to get a NyQuil hangover the following day. It starts working within 10 minutes to half an hour after its first dose. NyQuil gives you sound sleep when you are unable to sleep because of a cold or flu. Symptoms of the cold and flu are relieved, and you get a good night’s sleep.

But when you wake up the next day, you will be up with heavy eyes and a foggy feeling. It would feel like you were walking in molasses all around. The vision gets hazy. This is going to happen irrespective of the duration of sleep. You will be under the influence of NyQuil if you get up after 6 hours, 8 hours, or even 10 hours. In such a situation, one likes to try caffeine. But even caffeine does not work.

It is advised to take NyQuil every 6 hours, which gives a false indication that NyQuil does not last for more than 6 hours in our systems, but its side effects can be seen even after 10 hours of its dose.

NyQuil Dosage:

If you are an adult, you can take 30 mL every 6 hours if it is in liquid form.

If you give this to your children, then it becomes very important to ask the doctor.

Recommendations from a doctor about doses of NyQuil are preferred.

Following are the most common side effects of NyQuil:

  1. Difficulty in focusing
  2. Dizziness
  3. Drowsiness
  4. Fatigue
  5. Weakness
  6. Anxiety
  7. Excitability
  8. Loss of appetite
  9. Diarrhoea or constipation
  10. Upset stomach
  11. Nausea
  12. Vomiting
  13. Hangover

How long does NyQuil last?

Let’s learn about the half-lives of various ingredients in nyquil to get an idea of how long it stays in our bodies.

Acetaminophen: Half of it stays in the body of a healthy adult for around 2–3 hours. It gets flushed entirely from the system after 22 hours.

Dextromethorphan: The half-life of dextromethorphan is 3-6 hours, and it takes 11–33 hours for complete elimination from the body.

Doxylamine Succinate: Fifty percent of Doxylamine Succinate gets removed after 10 hours, and the whole of it takes around 2.25 days to clear up.

So it is clear that a substantial portion of nyquil is eliminated from the body after 10 hours of its consumption. Doxylamine succinate, which induces sleep, is the last one to get removed from the systemic circulation.

However, NyQuil stays in the bodies of different individuals for different durations depending upon the following factors:

  1. Age
  2. Metabolism
  3. Body Mass
  4. Amount and frequency of dosage
  5. Co-administration of other medicines

How long does NyQuil last in your system?

As it is told above in the article, it takes 6 hours for your system to release symptoms like drowsiness and sleepiness. It varies from person to person. For some people, drowsiness comes after 8 hours.

If we conclude it in short, then we would say you can do your work and other activities after around 10 hours. Sometimes it can be difficult to do your daily activities because of the sleepy effect of NyQuil.

If you face this situation, just wait and rest your body. It takes only 10 hours, and after that, you will feel good and active.

When NyQuil expires:

Although whenever you go and purchase NyQuil, no matter its liquid form or tablets, you see the expiration date on the label. Kindly check this date before using NyQuil.

Don’t use expired NyQuil because it loses its effectiveness once it gets expired. Some factors, like humidity and other environmental factors, reduce the expiration date of NyQuil.

Be extra aware while purchasing NyQuil, and be sure it is not expired.

How long does NyQuil stay in your system?

NyQuil contains several active ingredients, one of which is doxylaminе. The half-life of doxylaminе is approximately 10 hours, which means it can take up to 50 hours (or more than 2 days) for your body to totally eliminate doxylaminе from your system. However, the elimination time can vary depending on individual factors such as metabolism, age, and overall health.

How long does it take for NyQuil to kick in?

NyQuil is designed to kick in swiftly, generally within 30 minutes of consumption. This prompt action helps mitigate the discomfort associated with cold or flu symptoms and aids in ensuring restorative sleep, which is vital for the healing process. The quick onset of sleepiness and relief is what distinguishes Nyquil as a preferred option for many.


No matter how long NyQuil stays, it is for sure that you will start your day with heavy eyes and a little blurry vision. It is very important to give yourself at least 8 hours of sleep before starting the day. It is highly recommended not to drive or operate heavy machinery for at least 8 hours after administration.

One should be absolutely fine after 10 hours and can start day-to-day activities. If the hangover gets worse and you feel drowsy, heavy, and confused even after 10–12 hours, it is advisable to seek medical assistance.

By Caitlyn

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