How Long Does Nyquil Take to Work? It Depends - GoodRx (2024)

No one looks forward to a runny nose, headache, and coughing from the common cold or the flu. But thankfully, there are a lot of treatment options you can choose from. NyQuil Cold and Flu (acetaminophen/doxylamine/dextromethorphan) is one of many NyQuil products that can help relieve cold or flu symptoms. It’s available over the counter (OTC) in many brand-name and generic forms.

If you buy a NyQuil product, you may have questions about how to use it. How long will it take to work? And when should you take it?

What’s NyQuil?

NyQuil is an OTC medication that comes in many forms. This includes pills, liquid, and powder. It’s a combination product that contains several ingredients. Various Nyquil products may contain different ingredients. And the dose of each ingredient may vary between products. Always check the label to know exactly what’s in the specific NyQuil product you’re buying.

Active ingredients that might be in your NyQuil product include:

• Acetaminophen. This is also the active ingredient in Tylenol. It’s a pain reliever and fever reducer.

• Doxylamine. This is the active ingredient in Unisom SleepTabs. It’s an antihistamine. Antihistamines help with runny nose and allergies.

• Diphenhydramine. This is the active ingredient in Benadryl and Unisom SleepGels. It’s also an antihistamine.

• Dextromethorphan. This is the active ingredient in Delsym. It’s a cough suppressant that helps relieve cough symptoms.

• Phenylephrine. This is the active ingredient in Sudafed PE. It’s a decongestant that can help clear your sinuses and relieve a stuffy nose.

• Alcohol. Many Nyquil products contain alcohol. But alcohol-free versions may be available.

5 tips for taking NyQuil

If you’re able to, it’s a good idea to check with your healthcare provider before taking Nyquil. They can make sure it’s safe to take, based on your medical conditions. Below, we’ll answer common questions about taking Nyquil and offer some tips on what you can expect.

1. How long does it take NyQuil to work?

It may depend on what product you’re taking and what ingredients it has. For example, NyQuil Cold and Flu takes about 30 minutes to start working. It’s recommended that you take it every 6 hours, since the effects only last about 6 hours.

Even if you don’t feel symptom improvement after 30 minutes, don’t take an extra dose. Taking too much Nyquil can be dangerous. If your cold symptoms aren’t improving with the first few doses of Nyquil, talk to your healthcare provider.

It’s important to note that Nyquil isn’t meant to be used long-term. If you have any of the symptoms listed below, stop taking Nyquil and reach out to your healthcare provider. It may be a sign that something else is going on if you have a:

• Sore throat that lasts more than 2 days

• Fever that lasts more than 3 days

• Cough that lasts longer than 7 days

2. When is the best time of day to take NyQuil?

All NyQuil products contain a first-generation antihistamine like doxylamine or diphenhydramine. First-generation antihistamines are known to cause drowsiness. So although NyQuil can be taken during the day, it may make you sleepy.

If you’re going to take NyQuil products during the day, it’s important to avoid activities that require alertness. This includes driving. If you need to be alert throughout the day, consider using a non-drowsy medication and reserving NyQuil for nighttime.

DayQuil Flu and Cold is a medication that contains acetaminophen, dextromethorphan, and phenylephrine. It doesn’t contain an antihistamine, and it’s not known to cause drowsiness. This may be a better option for daytime use.

3. Should I take NyQuil with food?

You don’t have to take NyQuil with food. The ingredients in NyQuil aren’t known to cause nausea, so you may be OK to take it on an empty stomach, if that’s what you prefer.

4. Should I separate any medications from NyQuil?

No. But drug interactions are possible with Nyquil. These can happen whether you take your other medications at the same time as Nyquil, or whether you take them earlier or later in the day.

We’ll cover a few examples of important Nyquil interactions below. But keep in mind this isn’t a complete list. So be sure to let your healthcare provider or pharmacist know if you start taking NyQuil. Show them your current medication list so they can screen for possible drug interactions.

Monoamine oxidase inhibitors

Monoamine oxidase inhibitors (MAOIs) are medications that treat depression and Parkinson’s disease. Examples include isocarboxazid (Marplan), phenelzine (Nardil), and selegiline (Emsam, Eldepryl). The dextromethorphan in NyQuil can interact with MAOIs and cause serotonin syndrome.

Serotonin syndrome is a rare medical condition of too much serotonin. Serotonin is a chemical that’s involved in many bodily processes. Both dextromethorphan and MAOIs raise serotonin levels. Serotonin syndrome is usually mild, and may cause symptoms like tremor and sweating. It’s usually managed by stopping the medications that are causing it. But in severe cases, serotonin syndrome can be life-threatening. Serious symptoms may include agitation, high fever, and fast heart rate.

To avoid serotonin syndrome with MAOIs and Nyquil, you shouldn’t take Nyquil products that contain dextromethorphan within 2 weeks of an MAOI.

Other products that contain the same ingredients as Nyquil

Remember that Nyquil products contain a few different ingredients. If you take other OTC medications, it’s important to make sure you’re not taking too much of any one ingredient.

For example, Nyquil contains acetaminophen. Too much acetaminophen can cause nausea and vomiting. More seriously, it can cause liver damage. For most adults, the maximum acetaminophen dose is 4,000 mg per day. Taking more than this, from any source, raises your risk of liver damage.

Many NyQuil products also contain dextromethorphan. Taking too much dextromethorphan can cause heart problems, seizures, and even death. So make sure to avoid other products with dextromethorphan if you’re taking Nyquil

Warfarin

The acetaminophen in NyQuil can interact with warfarin (Coumadin, Jantoven). Acetaminophen may increase the international normalized ratio (INR) when taken with warfarin. The INR is a blood test that’s checked frequently in people taking warfarin. It tells you how well your blood is able to clot. A high INR means you have a higher chance of bleeding. If you’re taking warfarin, check with your healthcare provider before taking NyQuil.

Sedatives

Be careful combining NyQuil with other medications that cause drowsiness, like sedatives. Examples include benzodiazepines and other sleep medications. Other medications that cause drowsiness include OTC medications that contain diphenhydramine or doxylamine (which are also in some Nyquil products).

Taking Nyquil with other medications that can make you sleepy can cause excessive drowsiness and dizziness. You should also avoid alcohol while taking NyQuil because alcohol has sedative effects. And remember that some NyQuil products may also contain alcohol.

5. What can I do if I experience side effects from NyQuil?

The most common side effect of NyQuil is drowsiness. So it’s normal to feel tired after taking a dose of NyQuil. But strangely enough, NyQuil can also cause excitability in children. Though there are some children’s NyQuil products available on the market, talk to your child’s healthcare provider before giving them NyQuil if they’re under 12 years old.

NyQuil can also cause other side effects, like dry mouth, trouble peeing, and constipation. If you’re having bothersome side effects from NyQuil, you can stop taking it and check with your provider about how to best treat your cough and cold symptoms.