From the FDA Drug Label
Directions • take every 4 to 6 hours, or as directed by a physician• do not take more than 6 doses in 24 hours agedose Adults and children over 12 years of age10 mL (25 mg) to 20 mL (50 mg)
The maximum daily dose of Diphenhydramine (Benadryl) can be calculated based on the maximum number of doses allowed in 24 hours.
- For adults and children over 12 years, the dose is 10 mL (25 mg) to 20 mL (50 mg) per dose.
- The maximum number of doses in 24 hours is 6.
- Therefore, the maximum daily dose is 6 doses * 50 mg (maximum dose per intake) = 300 mg per day 1
From the Research
The maximum recommended daily dose of Benadryl (diphenhydramine) for adults and children 12 years and older is 300 mg per day, typically divided into doses of 25-50 mg taken every 4-6 hours, as supported by the most recent evidence 2.
Important Considerations
- Do not exceed 6 doses in 24 hours.
- For children 6-11 years old, the maximum is 150 mg per day, given as 12.5-25 mg every 4-6 hours.
- Benadryl should not be given to children under 6 years without medical supervision.
Rationale
These limits are important because exceeding them increases the risk of serious side effects including confusion, urinary retention, dry mouth, blurred vision, and in severe cases, hallucinations, seizures, or cardiac issues, as highlighted in a study on diphenhydramine overdose 2.
Special Populations
- Older adults should generally use lower doses as they're more sensitive to side effects.
- If you're taking other medications, especially those with sedative properties, check with your healthcare provider first as interactions can occur, as noted in a study on the metabolism of diphenhydramine 3.
Safety Precautions
- Benadryl causes drowsiness, so avoid driving or operating machinery after taking it.
- Be aware of the potential for diphenhydramine to cause loss of consciousness or seizures, as reported in a case study on diphenhydramine overdose 2.