Snooze University

Tylenol PM for Insomnia: Does It Work?

by Dale Cudmore | Updated: Feb 19, 2023

Current evidence suggests that normal Tylenol does not cause insomnia, and barely affects sleep at all.

But Tylenol PM is different, because it contains the antihistamine diphenhydramine hydrochloride in addition to acetaminophen, just like Benadryl.

Many older generation antihistamines like this one are known to make you sleepy, which is why it’s not surprising that some people take Tylenol PM to combat insomnia.

We’re going to look at research about this, along with whether or not it’s safe to do (spoiler: once in a while is okay, but frequent Tylenol use is dangerous).

Research About Diphenhydramine Hydrochloride and Sleeplessness

Common (affects 1-10% of people) side effects of diphenhydramine include (1):

  • Sleepiness
  • Drowsiness
  • Unsteadiness
  • Dizziness
  • Headache
  • Attention disturbance

So while it may not affect everyone in the same way, Tylenol PM will tend to be sleep promoting because of this.

However, it may cause dizziness or headaches in some people, which might make it harder to sleep, or affect sleep quality.

There isn’t too much research on the impact of diphenhydramine on sleep.

One study found that both valerian (a natural sleep aid) and diphenhydramine showed a “modest hypnotic effect” (2).

Another study that gave insomnia patients diphenhydramine found that (3):

The general condition of the patients with insomnia was at least “slightly improved” in 62.5% (12.5-mg group), 60% (25-mg group), and 67.4% (50-mg group) after treatment with the test drug for 2 weeks. Side effects were observed in a total of 11 patients (7.6%) but were not severe.

In other words, more diphenhydramine isn’t always better. Given the potential dangers of too much acetaminophen, there’s no reason not to stay on the safe side.

One other interesting finding from that study was:

The hypnotic effect of diphenhydramine hydrochloride was significantly greater in patients who had not been treated previously.

So taking Tylenol PM can be effective at improving insomnia severity at first, but the effectiveness will go down over time.

Finally, Pfizer funded a study (if anything they’d want positive results) that demonstrated a lack of robust clinical evidence supporting the safety and efficacy of diphenhydramine hydrochloride (4). Compared to other sleep medication and treatments, Tylenol PM should be a last resort, and not a regular medication.

SummaryTylenol PM does seem to make it easier to get to sleep, especially for people who are not used to it. However, the effect is relatively mild, and there are significant concerns about side effects and safety of long term use. However, if the acetaminophen in Tylenol PM also treats a symptom like a headache, it can provide effective short term sleep improvement.

Can Tylenol PM Make Sleep Worse?

While there aren’t a ton of studies, all the ones we looked at showed that diphenhydramine hydrochloride has a positive effect, if any, on getting to sleep.

There appears to be 2 potential ways that Tylenol PM could make sleep worse:

  1. A reaction to the acetaminophen - Some people have an allergic reaction to the main ingredient in regular Tylenol, and it can also interact with other drugs.
  2. Diphenhydramine hydrochloride can cause restless leg syndrome (RLS) - Certain antihistamines including diphenhydramine hydrochloride are known to cause RLS (5). It’s not surprising that there’s a link between restless leg syndrome and insomnia.

SummaryWhile it’s not particularly common, a small percentage of people may find it harder to sleep after taking Tylenol PM.

Summary: Does Tylenol PM Help Sleep Deprivation?

Tylenol PM may help insomnia in the short term, but it’s a quick fix and not a solution to insomnia (6).

Even though it’s an over the counter product, Tylenol PM (particularly the acetaminophen) can be dangerous even in small amounts if taken regularly and can lead to liver damage.

Insomnia should be treated by a doctor. There are other treatments that are safer and more effective, including actual sleep medication. More importantly, a doctor should be able to run tests and discover the root cause of your sleep issues.


  1. Diphenhydramine Side Effects
  2. Valerian-Hops Combination and Diphenhydramine for Treating Insomnia
  3. Clinical Evaluation of Diphenhydramine Hydrochloride for the Treatment of Insomnia in Psychiatric Patients
  4. Over-the-Counter Agents for the Treatment of Occasional Disturbed Sleep or Transient Insomnia
  5. Restless Legs Syndrome Fact Sheet
  6. Chronic Insomnia: A Practical Review

Medical Disclaimer: The information on is not intended to be a substitute for physician or other qualified care. We simply aim to inform people struggling with sleep issues about the nature of their condition and/or prescribed treatment.

About the authorDale is the founder of Snooze University and a sleep researcher. I overcame my sleep issues and now I'd like to help you do the same by summarizing the latest sleep studies for you.