What is the appropriate acetaminophen (Tylenol) dose and dosing interval for a 102‑lb (≈46 kg) individual?

Acetaminophen Dosing for a 102-lb (46 kg) Adult

For a 102-lb (46 kg) individual, take 650–1000 mg of acetaminophen every 6 hours, not exceeding 3000 mg per day for chronic use or 4000 mg per day for short-term use (≤10 days). 1, 2

Standard Dosing Regimen

• Single dose: 650–1000 mg (maximum 1000 mg per dose) 1, 2
• Dosing interval: Every 4–6 hours as needed 1
• Maximum daily dose:
  • 4000 mg per 24 hours is the FDA-approved maximum for short-term use 1, 3
  • 3000 mg per 24 hours is the recommended conservative limit for chronic administration (>7–10 days) to reduce hepatotoxicity risk 1

Critical Dosing Considerations

Duration-Based Limits

• Short-term use (≤10 days): Up to 4000 mg/day is acceptable in healthy adults without risk factors 1, 3
• Chronic use (>10 days): Limit to ≤3000 mg/day due to evidence showing 31–41% of healthy adults develop ALT elevations >3× normal at 4 g/day for 14 days 4
• If using beyond 7–10 days at 3000 mg/day: Monitor liver enzymes (AST/ALT) 1

Weight-Based Dosing Context

While your weight is 46 kg, adult acetaminophen dosing is not routinely weight-based for individuals within normal adult weight ranges 2. The standard adult dose of 650–1000 mg every 6 hours applies regardless of whether you weigh 46 kg or 70 kg 1, 2. Weight-based dosing (10–15 mg/kg) is primarily used in pediatric populations 5.

Mandatory Safety Precautions

Avoid Unintentional Overdose

• Check ALL medications for hidden acetaminophen content, including: 1, 4
  • Over-the-counter cold/flu remedies
  • Sleep aids (e.g., Tylenol PM)
  • Prescription opioid combinations (hydrocodone/acetaminophen, oxycodone/acetaminophen)
  • Other pain relievers marketed under different brand names
• The FDA limits prescription combination products to 325 mg acetaminophen per tablet specifically to prevent accidental overdose 1, 4

High-Risk Populations Requiring Dose Reduction

If any of these apply to you, reduce maximum daily dose to 2000–3000 mg/day: 1, 4

• Chronic alcohol use (≥3 drinks daily)
• Pre-existing liver disease or cirrhosis
• Malnutrition or fasting state
• Age ≥60 years (some guidelines recommend 3000 mg maximum) 1
• Concurrent use of other hepatotoxic medications 4

Practical Dosing Algorithm

For acute pain/fever (≤10 days):

1. Start with 650 mg every 6 hours 1
2. If inadequate relief, increase to 1000 mg every 6 hours 1, 2
3. Do not exceed 4000 mg in 24 hours 1, 3
4. Stop after 10 days unless directed by physician 3

For chronic pain (>10 days):

1. Use 650–1000 mg every 6 hours 1
2. Cap total daily dose at 3000 mg (e.g., 1000 mg three times daily or 650 mg four times daily) 1
3. If pain control inadequate at 3000 mg/day, add adjuvant therapies (topical agents, physical therapy, other analgesics) rather than increasing acetaminophen to 4000 mg 1
4. Monitor liver enzymes if continuing beyond 7–10 days 1

Common Pitfalls to Avoid

• Taking doses too close together: Maintain at least 4–6 hours between doses 1
• Combining multiple acetaminophen products: A single extra-strength tablet (500 mg) plus a cold medicine containing 325 mg acetaminophen taken four times daily = 3300 mg/day, exceeding safe chronic limits 1, 4
• Assuming "extra strength" means safer: Higher-dose tablets (500 mg) make it easier to accidentally exceed daily limits 6
• Continuing 4000 mg/day chronically: The 4000 mg FDA maximum is intended for short-term use; chronic administration should not exceed 3000 mg/day 1

When to Seek Immediate Medical Attention

Stop acetaminophen and seek emergency care if you develop: 4

• Nausea, vomiting, or abdominal pain (early toxicity signs)
• Yellowing of skin or eyes (jaundice)
• Dark urine or pale stools
• Confusion or unusual fatigue

Acetaminophen levels >200 mcg/mL at 4 hours post-ingestion or >50 mcg/mL at 12 hours indicate potential hepatotoxicity requiring N-acetylcysteine treatment. 4