Combination

Mixing DayQuil and Tylenol PM

CombinationCombination
Verdict

Unsafe · Acetaminophen twice

DayQuil and Tylenol PM both contain acetaminophen (Tylenol). This is the overdose people take by accident: each product stays under its own daily limit, and together they can go past it. Too much acetaminophen damages the liver, and symptoms may not start for 12 hours or more, so feeling fine does not mean the dose was fine. Every acetaminophen label says not to take it with any other product that contains acetaminophen.

  1. Take one of them, not both. Check the Drug Facts box on each: acetaminophen should appear on only one of them.
  2. Already took both and went past the daily limit? Call Poison Control now: 1-800-222-1222. Even if you feel fine. There is an antidote, and treatment within 8 hours gives a very good chance of recovery.
What “Unsafe” means
In an emergency, call 911911Never Use AlonePoison Control
What to do
  • Say what was taken and how much.Responders need it, and in most US states Good Samaritan laws protect both of you from drug possession charges when you call for an overdose.
  • Unresponsive: put them on their side, tilt the head back, and stay until help arrives.Never leave someone alone to “sleep it off”.
  • Never Use Alone 1-800-484-3731Stays on the line and sends help if you stop responding.
  • Full steps: what to do if it is already happeningOverdose signs, the recovery position, what to say on the call, and whether you can be charged for making it.
  • Poison Control 1-800-222-1222Free and 24/7, for “is this bad?” before it becomes an emergency.

Can you take DayQuil with Tylenol PM?

DayQuil contains acetaminophen and DXM. Tylenol PM contains acetaminophen and diphenhydramine. DayQuil and Tylenol PM both contain acetaminophen (Tylenol). This is the overdose people take by accident: each product stays under its own daily limit, and together they can go past it. Too much acetaminophen damages the liver, and symptoms may not start for 12 hours or more, so feeling fine does not mean the dose was fine. Every acetaminophen label says not to take it with any other product that contains acetaminophen. MixSafe rates DayQuil with Tylenol PM as "Unsafe" — risk of serious physical or psychological harm. Not recommended under any circumstances. Sources: the Drug Facts labels on DailyMed and the TripSit combination chart. Educational information, not medical advice.

What is in it

DayQuil
Acetaminophen + DXM. DayQuil also contains phenylephrine, a decongestant, and DayQuil Severe adds guaifenesin, an expectorant. MixSafe has no data for either.
Tylenol PM
Acetaminophen + Diphenhydramine.

Acetaminophen twice

Unsafe

DayQuil + Tylenol PM

What to do
  1. 01Take one of them, not both.Check the Drug Facts box on each: acetaminophen should appear on only one of them.
  2. 02Already took both and went past the daily limit? Call Poison Control now: 1-800-222-1222.Even if you feel fine. There is an antidote, and treatment within 8 hours gives a very good chance of recovery.
Signs it is happening
  1. Often nothing at firstThat is why it gets missed. Nausea, vomiting, sweating and stomach pain can follow; yellow skin or eyes mean the liver is already hurt.
Why this happens

DayQuil and Tylenol PM both contain acetaminophen (Tylenol).

This is the overdose people take by accident: each product stays under its own daily limit, and together they can go past it. Too much acetaminophen damages the liver, and symptoms may not start for 12 hours or more, so feeling fine does not mean the dose was fine. Every acetaminophen label says not to take it with any other product that contains acetaminophen.

Sources
  • Vicks NyQuil Cold & Flu, Drug Facts label: "Do not use with any other drug containing acetaminophen." DailyMed. dailymed.nlm.nih.gov
  • Acetaminophen overdose. MedlinePlus Medical Encyclopedia. medlineplus.gov

Ingredient by ingredient

  • DayQuil (DXM) + Tylenol PM (Diphenhydramine)Unsafe

    Diphenhydramine raises DXM levels, and together they risk serotonin syndrome, delirium, overheating and heart strain. Avoid this combination at recreational doses.

    The combination is reported to reduce the side effects of each drug and potentiate many of the recreational effects. There is a significant risk of serotonin syndrome, increased delirium, CNS depression, cognitive inhibition, risk of physical injury, hyperthermia, mania, paranoia, and psychosis, especially at higher dosages. There is an additional concern of tachycardia, hypertension, and in extreme cases, heart failure. Diphenhydramine is reported to inhibit the CYP2D6 enzyme which can increase levels of DXM. Medical dosages are not reported to be a concern. Caution is strongly recommended with this combination.

    Source: TripSit drug combination chart

    More on DXMMore on Diphenhydramine

Sources

Ingredient lists checked 2026-09-27. Formulas change and store brands differ, so the Drug Facts box on your own packet is the final word.

Think this is wrong, or know a better source? Send it.

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