How Long Does Nyquil Last (And Why)?

How Long Does Nyquil Last (And Why)?

Exact Answer: Six to Eight Hours

Insomnia or lack of sleep is a common phenomenon that several individuals face these days. There can be many underlying reasons for insomnia as stress, anxiety, or health issues. Patients who suffer from insomnia find it very difficult to fall asleep. 

Even when they finally sleep, they wake up after a short span and cannot sleep again. Several medications can help reduce the symptoms of insomnia. One of the most effective medicine is Nyquil. Taking Nyquil can make a person feel relaxed and sleepy. However, the effects of Nyquil are temporary.

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How Long Does Nyquil Last?

Nyquil is mainly a medication that is taken to treat cold or flu. It is amongst one of the best OTC (Over The Counter) medicines for cold. It is available in both pills as well as liquid solution forms.

Although it is a medication for treating cough, it can also have a relaxing effect. It can also cause drowsiness and may also induce the feeling of sleep. This feeling of drowsiness or sleepiness can last for about seven to eight hours in some cases.

The reason why a person is sleepy after taking Nyquil is Doxylamine Succinate, which is the main component in the making of Nyquil. Doxylamine Succinate is an antihistamine that blocks the histamine from getting attached to the receptors. This blockage of histamine causes drowsiness. It also makes the person feel asleep.

Nyquil can be used as an effective sleeping aid that can make a person feel sleepy for a maximum period of eight hours and a minimum period of four hours. The time for which Nyquil will last depends on many factors. For some people, it can give a sleeping effect of six hours. On the other hand, some may feel it for eight hours.

When Nyquil is taken, it gives a warm sensation to the throat. After around 10 minutes, the drowsiness will start to kick in. However, taking multiple doses should be avoided. Several doses in a less period can lead to health problems in the future like liver or kidney damage.

ReactionTime Taken
SleepinessAfter 30 minutes of ingesting Nyquil
Wearing offSix to eight hours

Why Does Nyquil Last For So Long?

Nyquil being an antihistamine, is very effective for flu or cough and cold. But it can also be used to help people who face problems in sleeping. The effects of Nyquil last differently for different people. There are a few reasons behind it, and they are as follows:

  • The foremost reason is that not all humans are the same, and the way medicine affects a person can be different from how it affects another individual. For some people, it might not even have an impact regards the feeling of drowsiness.
  • Another reason is the components of which Nyquil is made. It contains components like acetaminophen, doxylamine, and dextromethorphan. It can reduce pain and give the feeling of drowsiness. Due to these components, a person can sleep for a good six to eight hours at a stretch. 
  • The effects of Nyquil can also interfere with other medicines that a person might be taking. It can increase the time for which the person sleeps if it is taken with other medicines that have antihistamines as one of their key components.

Besides helping get sleep, Nyquil can also have a few side effects when taken more than the required limit. 


This medication can be addictive over time. Hence it becomes necessary to consume Nyquil only when it is prescribed by the doctor. Since Nyquil is an Over-the-counter medicine, it is easy to get access to the medication. If taken more than the required limit, it can also have many side effects.

However, prolonged use tends to diminish the effects. It might start taking more time to sleep. It will add to the existing stress and anxiety. In some cases, it can also begin affecting a person’s health over time.

Over usage of Nyquil can make a person feel tired and groggy even after sleeping for hours. It is also recommended not to have an alcoholic drink along with Nyquil as it can have adverse effects. 


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