Taking Nyquil With Dayquil
In our latest question and answer, our pharmacist discusses whether or not you can take Dayquil with Nyquil.
Can I take Nyquil and Dayquil together? I have quite a bad cold and I think I'm going to need medication to make me feel better.
May 13, 2022- You can take Nyquil and Dayquil on the same day, but you need to wait at least 4 to 6 hours between doses to avoid taking too much of the shared ingredients like acetaminophen.
- Both products contain 650 mg of acetaminophen per dose, and the safe daily limit is around 3000 to 4000 mg from all sources, so it's important to track your total acetaminophen intake across all medications.
- Nyquil contains a drowsy ingredient suited for nighttime use, while Dayquil contains a mild stimulant better for daytime use, so spacing them out also helps you avoid conflicting side effects.
The short answer here is that you can take them Nyquil & Dayquil together, but not at the same time. In this context, the "same time" means any time within 4 to 6 hours of one another.
So, in other words, it's fine to take them on the same day, just not at the exact same time.
DayQuil Ingredients
Dayquil Cold & Flu (the most common version) contains three active ingredients:
- Acetaminophen, a pain reliever
- Dextromethorphan, a cough suppressant
- Phenylephrine, a decongestant
Phenylephrine is a mild stimulant and can make some people jittery, which is less of a problem for daytime use.
Dayquil does not contain alcohol.
NyQuil Ingredients
Nyquil Cold & Flu also contains three active ingredients:
- Acetaminophen
- Dextromethorphan
- Doxylamine, an antihistamine related to the active ingredient in Benadryl (diphenhydramine).
Doxylamine can make you profoundly drowsy, so it’s better suited for nighttime use.
Nyquil Liquid also contains 10% alcohol, so one 30 mL dose contains a similar amount of alcohol as a shot glass of wine. The liquicaps do NOT contain alcohol.
Problems Taking NyQuil And DayQuil At The Same Time
The primary reason you don't want to take NyQuil and DayQuil at the same time is that they share some of the same drugs (e.g. dextromethorphan and acetaminophen).
The big concern here is taking too much acetaminophen as both contain 650 mg per dose (a dose of either product is 30 mL or 2 liquicaps)
Acetaminophen Concerns
Acetaminophen, a very common pain and fever reducer (found in Tylenol, for example), is broken down in the liver after you’ve taken it.
One of the chemicals it’s broken down into is toxic to the liver, but the body has a process for making it non-toxic and getting rid of it.
This process, however, has a limited capacity, and once that capacity runs out, the toxic byproduct can build up and cause severe liver damage (like, transplant-level, in serious cases).
That limit in a healthy, 150 lb person is around 4000 mg per day of acetaminophen from ALL sources, including pain relievers, prescription products, cough/cold/flu medications. For some people, the limit may be lower.
To keep yourself well in the clear, It’s best to take only the lowest amount necessary and stay around 3000 mg/day maximum.
If you have liver impairment or chronic diseases, talk to your doctor before using acetaminophen in any amount.
Four doses of Dayquil or Nyquil would deliver 2600 mg of acetaminophen per day, so you can see how quickly your daily dose adds up.
You don’t have to be afraid of the drug, but you do have to be smart and read the labels for all your medications.
You should also avoid drinking heavily (or ideally, at all) while using acetaminophen, meaning more than 2 drinks/day for men, and 1 drink/day for women.
Final Words
There you have it.
A good place to start if you want to use both products might be two doses of Dayquil and one dose of Nyquil daily.
If you need additional relief, you could instead take 3 doses of Dayquil, 1 dose of Nyquil, or two and two…whatever helps you avoid nighttime sleeplessness or daytime drowsiness.
Just be sure to always wait at least 4 hours between any dose of these products. Thanks for your question!
PS: If you’re taking the liquid form, use the dosing cup to measure 30 mL. Your cereal spoon is not accurate!
Glossary — Terms in This Answer
- Acetaminophen
- A common pain reliever and fever reducer found in products like Tylenol that is broken down by the liver.
- Dextromethorphan
- A cough suppressant ingredient found in both DayQuil and NyQuil.
- Phenylephrine
- A decongestant ingredient in DayQuil that works as a mild stimulant to help clear nasal passages.
- Doxylamine
- An antihistamine ingredient in NyQuil that causes drowsiness and is related to the active ingredient in Benadryl.
- Antihistamine
- A medication that blocks the effects of histamine in the body to reduce allergy and cold symptoms.
- Decongestant
- A medication that reduces nasal congestion by narrowing blood vessels in the nasal passages.
- Liver impairment
- A condition where the liver is not functioning properly and cannot process medications effectively.
- Toxic byproduct
- A harmful chemical created when acetaminophen breaks down in the liver that can damage liver cells.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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