Combining DayQuil & NyQuil For Nighttime Use

In our latest question and answer, the pharmacist discusses combining doses of NyQuil and DayQuil for use before bedtime.


NyQuil knocks me out and I mean way out! I tend to sleep through multiple alarms in the morning, etc. In an effort to alleviate some of that sleepiness, is it safe to take 15 ml of NyQuil and 15 ml of DayQuil at bedtime instead of a full 30 ml dose of NyQuil? Thank you!

Asked by Amanda On Nov 08, 2022

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Nov 08, 2022
Last updated Nov 08, 2022

Key points

  • It generally is not recommended to combine products that contain the same drugs due to the risk of accidental overdose.
  • DayQuil and NyQuil both contain acetaminophen and dextromethorphan.
  • Taking half-doses (i.e. half the normal dosage) of DayQuil and NyQuil will keep you in the recommended dosage range for all the drugs contained in the two products, but it is important to measure your doses carefully.


Both NyQuil and DayQuil share common ingredients so caution is advised when combining doses (to avoid overdose). However, one-half doses of each would be considered safe as you aren't going over the maximum dosage of any of the ingredients. You just need to be very careful to measure doses of each accurately.

Normally, you don't want to combine medications that share common ingredients. In fact, this is the way that most accidental overdoses occur.

For example, the number one reason for Tylenol (acetaminophen) overdoses is unknowingly combining two or more products that contain the drug.

However, as mentioned, since you are only taking half-doses of DayQuil and NyQuil, you are still in a safe dosage range for all the included medications.

Drugs In NyQuil & DayQuil

DayQuil contains the following ingredients:

  • Acetaminophen (pain reliever)
  • Dextromethorphan (cough suppressant)
  • Phenylephrine (nasal decongestant)

DayQuil bottle with drug facts label

NyQuil contains the following ingredients:

  • Acetaminophen (analgesic)
  • Dextromethorphan (cough suppressant)
  • Doxylamine (sedating antihistamine)

NyQuil bottle with drug facts label

As seen above, both products contain acetaminophen and dextromethorphan.

Full doses of NyQuil and DayQuil should not be taken together to avoid overdosing. Half-doses will keep you in a safe range.

Differences Between DayQuil And NyQuil

Below, are the main differences between DayQuil and NyQuil:

  • Phenylephrine (contained in DayQuil but not NyQuil)
  • Doxylamine (contained in NyQuil but not DayQuil)
  • Alcohol (NyQuil contains 10%, DayQuil is alcohol-free)

Phenylephrine is the nasal decongestant contained in DayQuil. It is not contained in NyQuil as it can cause insomnia or alertness in some individuals. Doxylamine is the antihistamine in NyQuil. It is added due to its sedative effect.

Combining DayQuil & NyQuil For Nighttime Use

While you could certainly combine DayQuil and NyQuil before bedtime (at appropriate dosages), it may not be as effective for sleep as NyQuil alone since DayQuil contains phenylephrine (nasal decongestant) and can cause insomnia in some people.

However, taking one-half dose of each will not result in too high of a dose of any single ingredient.  It is important to not take a full dose (30 ml) of each as this will result in a potential overdose of ingredients.

Taking half-doses (15 ml) of DayQuil and NyQuil will result in the following doses of each drug:

  • Acetaminophen 625 mg (325 mg from each)
  • Dextromethorphan 25 mg (15 mg from NyQuil, 10 mg from DayQuil)
  • Phenylephrine 5 mg (from DayQuil)
  • Doxylamine 6.25 mg (From NyQuil)

All the above doses are within the range of an acceptable single dose of each ingredient.

Final Words

Thanks for reaching out to us!


  • Acetaminophen Toxicity, NIH
  • Concomitant overdosing of other drugs in patients with paracetamol poisoning, PubMed
  • Acetaminophen Monograph, PubChem
  • DayQuil/NyQuil Manufacturer Website, Vicks

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 11 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Feel free to send him an email at! You can also connect with Dr. Brian Staiger on LinkedIn.

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