How Long Does It Take For Nyquil To Kick In

How long does it take for Nyquil to kick in?

Nyquil is a common over-the-counter (OTC) medicine used temporarily to treat symptoms of cold and flu like fever, cough, sore throat, and runny nose. It also helps to relieve allergies or other breathing illnesses such as sinusitis and bronchitis.

Different drugs have different ways they work in different people. Some people will feel the effect as soon as they take the drug, while for others it might take a while. Since that’s the case, how long does it take for Nyquil to kick in?

Several factors could affect how long it will take for Nyquil to kick in, which we’ll be discussing in this article, along with other facts you will find interesting to know about Nyquil.

How to Take Nyquil

Nyquil is available both in capsules and oral form. Directions on how to take any form of the drug are usually written on the patient’s information leaflet inside the packet of the drug, or you could ask your local pharmacist or doctor for directions on how to take the drug.

However, the typical dosing for the liquid form of Nyquil is:

  • For adults and Children 12 Years and Above: 30 ml (2 tablespoons) taken orally every 6 hours.
  • For Children 4-11 Years Old: Dosing depends solely on their doctor’s prescription. Children who are younger than this should not be given Nyquil.

Meanwhile, the typical dosing for the capsule form of Nyquil is:

  • For adults and Children 12 Years and Above: 2 capsules, taken daily every 6 hours, until your prescription is over.
  • For Children 4-11 Years Old: Dosing depends on their doctor’s prescription, and children younger than this should not be given the drug.

Regardless, dosing can differ from person to person, depending on the Nyquil product you’re using and your response to treatment, don’t increase or reduce your dose, or take it more or less frequently than you should, as improper use of the drug may result in serious harm like brain damage and seizure.

Nyquil can be taken with or without food, but if you have a stomach upset taking it without food, it may help to take it with food or milk. Don’t crush or chew the capsule, doing that can release all the drug content at once, hence increasing the risk of side effects. Swallow the drug whole with milk or water.

Don’t take Nyquil with alcohol or marijuana, as doing that can increase the risk of side effects. Also don’t take Nyquil if you’re allergic to any of the ingredients, active or inactive. Let your doctor know of your allergies before taking this drug.

 If you have any medical condition, let your doctor know about it before taking Nyquil, as certain medical conditions may get worse with this drug. Medical conditions such as asthma, diabetes, glaucoma, kidney failure, liver disease, ulcer, hyperthyroidism, urinary retention, enlarged prostate, and heart problems.

Under these conditions, Nyquil may pose a serious threat to your health. For instance, some Nyquil products may contain sugar or alcohol, so a diabetic or someone with a liver problem might be endangering himself further.

Nyquil Ingredients

The content of a drug contributes to its effectiveness, Nyquil, there are different versions of it on the market.

However, the most common versions contain the following active ingredients:

  • Acetaminophen: An analgesic and fever reducer
  • Dextromethorphan: A cough suppressant 
  • Doxylamine: An antihistamine for relieving symptoms of allergies

Some Nyquil products such as Nyquil Severe may contain additional active ingredients such as phenylephrine, a nasal decongestant. The combination of all these active ingredients contributes to making Nyquil an effective cold and flu medicine.

How Long Does It Take For Nyquil To Kick In
How Long Does It Take For Nyquil To Kick In?

How Does Nyquil Work?

All three active ingredients in Nyquil work differently to give you the relief you need.

Acetaminophen relieves pain and reduces fever by blocking the production of certain chemicals that causes both pain and fever, Dextromethorphan, on the other hand, calms the part of your brain that makes you cough, thereby making you cough less, and Doxylamine blocks the production of histamine, a natural chemical your body produces when you come in contact with an allergy.

How Long Does It Take for Nyquil to Kick in?

It usually takes 30 minutes for Nyquil to kick in and you begin to notice relief from your symptoms but this could be different for you.

How long it kicks in depends on some factors such as:

  • Biological sex: Females tend to have a lower rate of metabolism than males, therefore, it may take longer for Nyquil to kick in for them as they have lesser body water to dilute drugs faster.
  • Body Weight: Your body weight can also influence your rate of metabolism, hence slow metabolism will require more time before Nyquil kicks in, and vice versa. 
  • How You Take It: It is advisable to take Nyquil with a lot of water as it will help to loosen the mucus in your lungs. Also, the liquid form of Nyquil might kick in faster than the capsule form, since it can be easily absorbed by the body.
  • Other Medications: Certain drugs or supplements you take might interact with Nyquil, thereby affecting its effectiveness and so making it take longer time to kick in.

How Many Hours Does Nyquil Work for?

Nyquil approximately works 6 hours, which is why the dosing instruction usually says “in every 6 hours” since symptom relief lasts about 6 hours per dose. Nyquil stays in your body for 6 hours after you’ve taken it, so, within these 6 hours, it’s advised that you don’t take another dose or it becomes overdosing, and that becomes a problem as the risk of experiencing severe side effects increases.

Side Effects of Nyquil

Some of the common side effects of Nyquil are:

  • Dizziness
  • Stomach upset
  • Drowsiness
  • Diarrhea 
  • Nausea
  • Fatigue
  • Hangover
  • Anxiety
  • Vomiting
  • Loss of appetite
  • Constipation
  • Weakness
  • Dry mouth or throat 
  • Blurred vision

In cases of severe side effects, you may experience:

  • Hallucination
  • Mood changes
  • Trouble urinating
  • Shaking
  • Irregular heartbeat 
  • Severe allergic reactions such as rash, itching, swelling of the face or tongue, severe dizziness, and difficulty breathing.

If you experience these or any discomfort while taking Nyquil, let your doctor or pharmacists know immediately. Most times these side effects are temporary, but should they persist or worsen, it is best to let your doctor or pharmacist know also.

How Long Does Nyquil Take to Make Me Sleep

Along with the symptom relief, you’ll feel after 30 minutes of taking Nyquil, you’ll begin to experience its side effects such as drowsiness and dizziness much later after the sedating ingredient in the drug –doxylamine has reached its peak, which is around 2-3 hours, although it varies in different people, depending on your body.

This effect generally, could last for 6-8 hours because the doxylamine can last up to 8 hours in the body, however, this is what makes nighttime the ideal time to take Nyquil.  

If the sleepy feeling of Nyquil should last for more than 6-8 hours, there’s a chance you’ll wake up groggy the next morning.

How Long Does It Take Nyquil to Wear Off?

Just as we’ve said, it takes approximately 6-8 hours for Nyquil’s effect to last, so we can say that after about 10 hours of taking the drug, it must have worn off and you should be strong and active enough to carry out your activities, however, this is not definite as it could vary from person to person.

When Is the Best Time to Take Nyquil?

Because of the side effects of Nyquil, it is best taken at night, when you are no longer active or you don’t have to drive or operate a machine, so you don’t fall into any accidents because you’re either dizzy, drowsy, or have a blurry vision.

How Long Before Nyquil Leaves Your System

The time it takes for any drug to leave your system depends on the half-life of each active ingredient in the drug. For Nyquil, the half-live of each active ingredient is different, so learning about their half-lives will help in determining how long Nyquil will take to leave your system.

  • Acetaminophen: For a healthy body, half of it stays in the body for 2-3 hours and gets entirely flushed out of your system after 22 hours.
  • Dextromethorphan: The half-life of dextromethorphan is 3-6 hours but entirely leaves the system after 11-33 hours.
  • Doxylamine: Half of doxylamine leaves your system after 10 hours and after 2.25 days, it gets completely flushed out.


Nyquil is a temporary treatment for symptoms of cold and flu, how long it would take for Nyquil to kick in will differ for different individuals due to certain factors such as biological sex and body weight, although approximately it should take about 30 minutes for Nyquil to kick in.

Along with feeling relief from your symptoms, Nyquil also causes dizziness and drowsiness, although these kick in some hours after you’ve taken the drug. Let your doctor know if after 1 week of treatment and you don’t feel any relief, your symptoms may be indicating more severe medical problems.

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