How Long Does Nyquil Last?

In this article, our pharmacist answers the question: How long each dose of Nyquil last?

Nov 03, 2017

Whitny asked

How long does Nyquil last? Will it last all night?


All versions of Nyquil (e.g. Cold & Flu, Severe) last around four to six hours per dose.

The most common version of Nyquil is Nyquil Cold & Flu. It contains the following ingredients:

  • Acetaminophen: Pain reliever and fever reducer
  • Dextromethorphan: Cough suppressant
  • Doxylamine: Sedating antihistamine

Each dose of Nyquil Cold & Flu will begin to work about 15-30 minutes. However, the sedating ingredient in the medication (doxylamine) reaches peak blood around 2-3 hours after administration. This is why the onset of sedation may be somewhat slow to take effect.

While the average dose of Nyquil lasts an average of 4-6 hours, doxylamine can have a slightly wider range of effect. Depending on the person, it can last anywhere from 3 to 8 hours, making it an ideal choice as a night time sedative. Any longer, and there would be a high chance of morning grogginess.

Below, we list the other common versions of Nyquil:

Nyquil Severe contains the following ingredients:

  • Acetaminophen
  • Dextromethorphan
  • Doxylamine
  • Phenylephrine

Nyquil severe adds the ingredient phenylephrine, a nasal decongestant. Nyquil severe also lasts around 4-6 hours per dose. Some find Nyquil Severe not quite as sedating as Nyquil & Flu because phenylephrine has a mild stimulant effect.

    Nyquil Cough contains the following ingredients:

    • Doxylamine
    • Dextromethorphan

    Nyquil Cough simply omits acetaminophen as an ingredient. It also will last around 4-6 hours per dose.

    Ready for a more personal experience with your meds?