Mixing Codeine (lean) and DayQuil
Dangerous
High risk of death or life-changing injury. Do not combine.
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”.
- Give naloxone (Narcan) if you have it.It is sold over the counter in every US state and does no harm if opioids turn out not to be involved.
- 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 Codeine with DayQuil?
DayQuil contains acetaminophen and DXM. The most concerning part is Codeine with DayQuil (DXM): together they slow breathing and strain the heart and liver, and DXM makes the opioid hit harder. Do not combine. Keep naloxone nearby. MixSafe rates Codeine with DayQuil as "Dangerous" — high risk of death or life-changing injury. Do not combine. Sources: the Drug Facts labels on DailyMed, the TripSit combination chart and MixSafe research. 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.
Ingredient by ingredient
Codeine + DayQuil (DXM)Dangerous
Together they slow breathing and strain the heart and liver, and DXM makes the opioid hit harder. Do not combine. Keep naloxone nearby.
CNS depression, difficult breathing, heart issues, hepatoxic, just very unsafe combination all around. Additionally if one takes DXM, their tolerance of opiates goes down slightly, thus causing additional synergistic effects.
Class-level answer, inherited from Opioids. Nothing specific to this exact pair is documented, so treat it as the default for the class rather than a measurement of this drug.
Source: TripSit drug combination chart
Codeine + DayQuil (Acetaminophen)Caution
Most codeine tablets already contain acetaminophen, so more codeine means more acetaminophen, and liver damage gives no warning for a day or more. Check the label and count every source.
Not an interaction between the drugs so much as a counting problem that sends people to hospital. Most codeine sold over the counter is a combination tablet, so escalating the codeine escalates the paracetamol in lockstep. Eight co-codamol tablets is already 4g of paracetamol — the entire daily ceiling — and liver injury from that has no warning symptoms for a day or more, by which point it is well advanced. Add any separate paracetamol and you are over. If you are taking codeine at above-label doses, use a single-ingredient formulation.
Sources: Prescott LF. Paracetamol, alcohol and the liver. Br J Clin Pharmacol. 2000 · Acetaminophen: A Liver Killer or Thriller
- Vicks DayQuil Cold & Flu LiquiCaps, Drug Facts label. DailyMed. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=efb982d4-93d0-815f-e053-2995a90a82dd
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.
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