**General guidelines for a healthy adult:**
- **FDA/prescription labeling maximum: 4,000 mg per 24 hours**
- **Manufacturer OTC labels are more conservative:** Extra Strength Tylenol (500 mg tablets) caps at 3,000 mg/day; Regular Strength (325 mg) caps at 3,250 mg/day. These lower limits build in a safety margin for accidental overshoot.
- **Many clinicians recommend staying at or below 3,000 mg/day**, especially for regular or long-term use.
**Practical dosing:** 325–1,000 mg every 4–6 hours, with at least 4 hours between doses and no more than 1,000 mg in a single dose.
**Important cautions:**
- **Watch for hidden acetaminophen.** It's in hundreds of combination products — cold/flu remedies (NyQuil, Theraflu), sleep aids (Tylenol PM), and prescription opioids (Percocet, Norco, Vicodin). Accidental double-dosing from these is the most common cause of acetaminophen liver injury.
- **Alcohol increases risk.** If you drink regularly (3+ drinks daily), the safe ceiling is lower — talk to a clinician; many suggest 2,000 mg/day or avoiding it.
- **Lower limits apply** if you have liver disease, are malnourished or fasting, weigh under ~50 kg, are elderly, or take warfarin or certain seizure medications.
- **Overdose is deceptive** — you may feel fine for 24+ hours while liver damage progresses. If you suspect an overdose, call Poison Control (1-800-222-1222 in the US) immediately; the antidote works best within 8 hours.
This is general information — check with your pharmacist or doctor about your specific situation, particularly if you're taking other medications or using acetaminophen for more than a few days.