Can The Effects Of Benadryl Last Into The Next Day?

In our latest question and answer, the pharmacist discusses how the effects of Benadryl (diphenhydramine) can last longer than intended and cause a "hangover" effect.


I am 68 years old, I have been taking Benadryl (diphenhydramine ) for a sleeping aid for several months. Today, I woke up dizzy, disoriented and I felt this way all day... will these symptoms go away by tomorrow morning?

Asked by scott On Mar 30, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Mar 31, 2018

Benadryl (diphenhydramine) is a commonly used over the counter treatment for insomnia due to its sedative effects. While somewhat effective in decreasing sleep latency (i.e. time it takes to fall asleep), it hasn't been found to be very effective for increasing total sleep time and is associated with a variety of side effects such as:

  • Dry mouth
  • Dry eyes
  • Constipation
  • Next day grogginess
  • Dizziness
  • Next day sedation

Benadryl (Diphenhydramine) Next Day Drowsiness

For most individuals, after taking by mouth, the sedative effects of Benadryl will begin to occur in 20-45 minutes. Peak sedatory effects are reported to occur around 1 to 2 hours after dosing.

The usual duration of action of Benadryl is 4 to 6 hours but this can be greatly increased in older adults.

Benadryl use, especially in the elderly, has been associated with next day grogginess. This is sometimes known as a "hangover" effect or "Benadryl hangover".

Although Benadryl generally only lasts 4 to 6 hours for most individuals, a variety of studies, such as this one, have reported next day grogginess and hangover effects in many individuals.

Some studies have gone as far as to verify that Benadryl (diphenhydrmaine) is still bound to receptors in the brain the next morning after night time dosing in certain individuals, which could lead to sedative effects.

Most data indicates that as we age, metabolism of many drugs, including Benadryl slows down. For example, one study found that the half-life (i.e. time it takes for 50% of a drug to be metabolized) of Benadryl is nearly tripled in the elderly when compared to children. Specifically, the study found the half life of Benadryl to be the following in different age groups:

  • Children: ~5.5 hours
  • Young Adults: ~9.2 hours
  • Elderly: ~13.5 hours

Genetic differences in individuals can also be a significant factor in how quickly individuals metabolize medication.

If you do feel next day grogginess or a "hangover" feeling on Benadryl, know that the effects are not uncommon. In most cases, the effects should dissipate throughout the day and should not last more than a day or two.

Benadryl (Diphenhydramine) Sleep Recommendations

Most guidelines, such as those from the American Academy Sleep Medicine, don't recommend using Benadryl for insomnia due to insufficient evidence for benefit and the potential side effects. 

If you have been using Benadryl and have had problems with next day drowsiness, speak with your doctor regarding possible alternatives.

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Office: 716-389-3076

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