Can I take DayQuil and NyQuil together?

Why can't I take DayQuil and NyQuil at the same time?

They share 2 of their active ingredients. Standard DayQuil and NyQuil both contain acetaminophen, a pain reliever and fever reducer, and dextromethorphan, a cough suppressant. Each one then adds 1 ingredient the other does not have.

Both labels say not to use the product with any other medicine that contains acetaminophen. The other Quil counts. Taking a dose of each together gives you 2 doses of acetaminophen and 2 doses of cough suppressant at once.

The numbers below come from the current DailyMed labels for standard DayQuil Cold and Flu LiquiCaps and NyQuil Cold and Flu liquid. Other versions, such as Severe, can contain different ingredients and amounts, so check the Drug Facts on your own box.

• DayQuil Cold and Flu LiquiCaps (per 2-capsule adult dose): acetaminophen 650 mg, dextromethorphan 20 mg, phenylephrine 10 mg (a decongestant)
• NyQuil Cold and Flu liquid (per 30 mL adult dose): acetaminophen 650 mg, dextromethorphan 30 mg, doxylamine 12.5 mg (a sedating antihistamine)
• Shared: acetaminophen and dextromethorphan
• Only in DayQuil: phenylephrine. Only in NyQuil: doxylamine, a sedating antihistamine that carries the drowsiness warning

How long after DayQuil can I take NyQuil?

The labels do not give a separate switching rule, so the cautious way to read them is to treat DayQuil and NyQuil as 1 medicine for timing. Before your next dose, wait at least the interval printed on the box of the dose you just took.

For the standard adult products, that means at least 4 hours after DayQuil, because the DayQuil label says every 4 hours. Wait at least 6 hours after NyQuil before DayQuil, because the NyQuil label says every 6 hours. A standard adult dose of either product has the same 650 mg of acetaminophen, so taking NyQuil 4 hours after DayQuil keeps the acetaminophen on the same schedule DayQuil allows on its own.

Intervals are not the same on every version. Some LiquiCaps and kit versions use different timing, so read the directions on the box you have, not the one you remember.

• After standard DayQuil: wait at least 4 hours before NyQuil
• After standard NyQuil: wait at least 6 hours before DayQuil
• Never: a dose of each at the same time

How many doses can I take in a day if I use both?

The DayQuil label caps you at 4 doses (8 LiquiCaps) in 24 hours. The NyQuil label caps you at 4 doses in 24 hours. Both labels say severe liver damage may happen if you go over that. The labels do not say whether those limits are separate when you use both products, so count every DayQuil and NyQuil dose together toward 1 limit of 4 doses in 24 hours. Treating the limits as separate could mean 8 doses, which is 5,200 mg of acetaminophen, well over the FDA's 4,000 mg daily adult maximum.

With standard adult doses, 4 total doses adds up to 2,600 mg of acetaminophen. That leaves room under the FDA's 4,000 mg daily adult maximum from all medicines combined, but that 4,000 mg is a ceiling, not a target. Any other acetaminophen you take, such as Tylenol or a prescription pain medicine that contains it, adds to the total. On labels it can also be listed as APAP.

Here is one example of a day that stays inside these rules for an adult using standard products. Your times can be different as long as you keep the gaps and the total.

• 8 am: DayQuil (dose 1)
• 12 pm: DayQuil (dose 2)
• 4 pm: DayQuil (dose 3)
• 10 pm: NyQuil (dose 4)
• Next dose: not before 8 am, when the first dose drops out of the last 24 hours

Who should ask a pharmacist or doctor first?

Some people should check before taking either product, even on its own. The labels list these.

Both products also say: if you are pregnant or breastfeeding, ask a health professional before use. For children, the DayQuil LiquiCaps and NyQuil liquid labels say adults and children 12 and over can use them, children 4 to under 12 should ask a doctor, and children under 4 should not use them. DayQuil liquid has its own dose for children 6 to under 12, so check the box. The timing and dose rules on this page are for adults and children 12 and over.

• Do not use either if you take a prescription MAOI (certain drugs for depression, psychiatric or emotional conditions, or Parkinson's disease) or stopped one in the last 2 weeks
• Liver disease, or 3 or more alcoholic drinks a day: acetaminophen can cause severe liver damage
• High blood pressure, heart disease, thyroid disease or diabetes: DayQuil (it contains the decongestant phenylephrine)
• Glaucoma or a breathing problem: NyQuil
• Trouble urinating from an enlarged prostate, a chronic cough (such as from smoking, asthma or emphysema), or a cough with a lot of mucus: both
• Taking warfarin, or (for NyQuil) sedatives or tranquilizers

What about drowsiness, alcohol and driving?

DayQuil has no antihistamine, and its label has no drowsiness warning. NyQuil contains doxylamine, and its label warns that marked drowsiness may happen. Alcohol, sedatives and tranquilizers can make that drowsiness worse.

The NyQuil label says to avoid alcoholic drinks and to use caution when driving or operating machinery. Take NyQuil when you are done for the day, not before a drive. If you still feel drowsy in the morning, do not drive until it passes.