Diphenhydramine
We’ll deliver to you in 2-5 days
Price checker
$79.95
  • Prices include:
    Express shipping

    2-5 day shipping by secure courier

  • Consultation + Access to our clinicians

    Ask our experts anything you like, any time you want.

  • Total
    $79.95
    Save $0.00 each order
Reviewed on February 20, 2025. by
Dr. Joseph Palumbo
Senior Medical Adviser
Registered with NPI (No. 1043478878)
Next review due on
February 20, 2028.
Dr. Joseph Palumbo

Last updated on Feb 19, 2025.

Product info

  • Diphenhydramine is available as 25mg and 50mg tablets.

  • Take one tablet by mouth at bedtime.
  • It’s quickly absorbed and starts working in about 30 minutes.

Price checker
$79.95
  • Prices include:
    Express shipping

    2-5 day shipping by secure courier

  • Consultation + Access to our clinicians

    Ask our experts anything you like, any time you want.

  • Total
    $79.95
    Save $0.00 each order
Diphenhydramine Diphenhydramine

What is Diphenhydramine?

Diphenhydramine is an antihistamine drug that’s commonly used as an over-the-counter nighttime sleep aid due to its sedative effects. Diphenhydramine has been found in clinical trials to be effective in decreasing the time it takes to fall asleep (sleep onset) and and improves both the depth and quality of sleep.[4]

Diphenhydramine is also the active ingredient in Benadryl, a drug commonly used to relieve symptoms of allergy, hay fever or the cold. It’s also less commonly used to treat motion sickness and tremors in Parkinson’s disease. 

How does Diphenhydramine work?

Diphenhydramine is an antihistamine, which means that it works by blocking a chemical called histamine from binding to H1 receptors in the body. This property is mostly responsible for its effects on relieving allergy symptoms, although experiments in mice revealed that its interactions with H1 receptors play a key role in promoting sleep.[1]

Diphenhydramine’s sedative effects also come from its ability to cross the blood-brain barrier, a protective layer around the brain. Once inside, it blocks NMDA receptors (chemicals involved in memory and learning), which leads to increased drowsiness and reduced alertness.[2][3]

What forms of Diphenhydramine are there?

Diphenhydramine comes as 25mg and 50mg tablets for insomnia. For other conditions like allergies, it’s available as a tablet, a capsule, a rapidly disintegrating tablet, a dissolving strip, a liquid, a liquid-filled capsule, and a powder. It’s also used in addition to epinephrine for anaphylaxis (sudden, life-threatening allergic reaction) as an injection. 

Topical formulations, including creams, gels, lotions, sprays, and eye drops, are also available, where diphenhydramine is often used in combination with other ingredients like zinc acetate. 

Treated trusted source:

  1. Wang, Y.-Q., et al. (2015). Doxepin and diphenhydramine increased non-rapid eye movement sleep through blockade of histamine H1 receptors. Pharmacology Biochemistry and Behavior, 129, pp.56–64.
  2. Roth, T., et al. (1987). Sedative effects of antihistamines. Journal of Allergy and Clinical Immunology, 80(1), pp.94–98.
  3. Föhr, K.J., et al. (2015). Open channel block of NMDA receptors by diphenhydramine. Neuropharmacology, 99, pp.459–470.
  4. Rickels, K., et al. (1983). Diphenhydramine in Insomniac Family Practice Patients: A Double-Blind Study. The Journal of Clinical Pharmacology, 23(5-6), pp.234–242. 
treated.com This page was written by The Treated Content Team.
Dr. Joseph Palumbo
This page was medically reviewed by Dr. Joseph Palumbo on February 20, 2025. Next review due on February 20, 2028.

How we source info.

When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.

Diphenhydramine Diphenhydramine

How to take Diphenhydramine for insomnia?

Take one whole tablet with a full glass of water before bed. Don’t crush or chew the tablets. Also, try to go to bed within approximately 20 minutes after taking the tablet to avoid the risk of injury, as Diphenhydramine can make you drowsy and less alert.

The recommended dose for adults is generally up to 50mg of Diphenhydramine a day, but your physician will tell you what dose and how to take it.

How long does it take for Diphenhydramine to work?

One oral dose of Diphenhydramine is absorbed quickly into your system. You’ll likely start feeling drowsy after about half an hour, and it reaches peak concentration in the blood after about two hours.[1] These effects will last from four to six hours, helping you to experience more restful sleep.

What if I make a mistake while taking Diphenhydramine?

If you take too many Diphenhydramine tablets, then you’re more likely to experience side effects like dilated pupils, fever, a faster heartbeat, seizures, jerky movements, dry mouth, fatigue, sleepiness, confusion, blurry vision, uncontrolled shaking, or hallucinations.

A large overdose may cause excessive muscle breakdown, leading to seizures, kidney problems, irregular heartbeats, losing contact with reality, or coma.

In these cases, it’s important to call 911 or go to the nearest emergency department. And if possible, take the pack and the remaining pills with you.

Treated trusted source:

  1. Blyden, G., Greenblatt, D., Scavone, J., & Shader, R. (1986). Pharmacokinetics of Diphenhydramine and a Demethylated Metabolite Following Intravenous And Oral Administration. The Journal of Clinical Pharmacology, 26.
treated.com This page was written by The Treated Content Team.
Dr. Joseph Palumbo
This page was medically reviewed by Dr. Joseph Palumbo on February 20, 2025. Next review due on February 20, 2028.

How we source info.

When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.

Diphenhydramine Diphenhydramine

Diphenhydramine isn’t suitable for everyone, and there are some things that you need to be aware of when taking it.

Here’s all the official info on it. If anything is unclear, let our experts know, and they can talk with you about it.

Diphenhydramine Diphenhydramine

Diphenhydramine: FAQ

Have something specific you want to know? Search our info below, or ask our experts a question if you can’t find what you’re looking for.

Is Diphenhydramine different from other over-the-counter medications for insomnia?

Answer:
Besides Diphenhydramine, other over-the-counter medications include doxylamine and melatonin. Diphenhydramine and doxylamine (Unisom) are both antihistamines with sedative effects, but doxylamine is often considered longer-acting and potentially more sedating. This means it may stay in your system longer, increasing the risk of next-day drowsiness compared to diphenhydramine.

Melatonin is a natural hormone that helps regulate the body’s sleep-wake cycle. Unlike diphenhydramine, which induces drowsiness by blocking histamine receptors in the brain, melatonin works by signaling to your body that it’s time to sleep. Melatonin is generally a safer option for older adults and people who need to use it long-term, whereas diphenhydramine is best for short-term sleep aid due to potential side effects like tolerance and next-day drowsiness.

Is Diphenhydramine addictive?

Answer:
It can be when you take more than you should or if you take it for too long. It’s possible to become psychologically addicted to it, and rely on it for sleep. Over time, some people can also find that they’ll build up a tolerance and start needing higher doses of Diphenhydramine for it to work, which indicates that they may have become dependent on it.

Withdrawal symptoms are milder than those for other drugs, but can still be unpleasant and include nausea, cold sweats or diarrhea.

Can I take Diphenhydramine in combination with other medications I’m using?

Answer:
Generally, it’s recommended to tell your healthcare provider before taking Diphenhydramine with any of these medications, because using them together can increase your risk of experiencing side effects:

  • treatments for depression like mirtazapine (Remeron), fluoxetine (Prozac), phenelzine (Nardil), venlafaxine (Effexor), bupropion (Wellbutrin), or amitriptyline (Elavil, Vanatrip);

  • other antihistamines used in cold and cough medications like clorpheniramine;

  • sedatives like Diazepam and hypnotics like Nitrazepam;

  • medications for high blood pressure like metoprolol;

  • medications that relax smooth muscles used to treat Parkinson’s, IBS or urinary incontinence.

Does Diphenhydramine have side effects?

Answer:
It can cause some side effects, but you might not be affected by any of them. Common side effects include drowsiness, sedation, dizziness, inability to concentrate, unsteadiness, dry mouth, tiredness.

Other unwanted effects may include:

  • headaches;

  • sensation of pins and needles;

  • confusion;

  • nervousness, restlessness (usually, older people are more prone to these side effects);

  • blurred vision;

  • vomiting;

  • nausea;

  • muscle twitches;

  • depression;

  • difficulty in passing urine; or:

  • sleep disturbances.

Can you take Diphenhydramine while pregnant?

Answer:
While it can be used in pregnancy, Diphenhydramine can cross the placenta,[1] so it’s not generally recommended. You should always talk to your doctor before using it if you’re pregnant or planning to have a baby, as other options like cognitive behavioral therapy may be more suitable for you.

You can also start by avoiding blue light from screens, trying relaxation techniques, implementing a sleep routine, and avoiding naps.

Treated trusted source:

  1. Stellpflug, S.J., Bangh, S.A. and Cole, J.B. (2018). The treatment of maternal and fetal anticholinergic toxicity with physostigmine. Toxicology Communications, 2(1), pp.35–38. 

This is healthcare on your terms.

All from the comfort of your device. Get access to what you need, when you need it.

100% online

Ask questions and get expert recommendations, at the touch of a button.

Tailored choices

We'll narrow down some treatments for you to choose from based on your medical profile.

Secure shipping

Receive your treatment by express delivery, in discreet packaging.

Easy automatic refills

Set your own delivery schedule and pause or make changes any time you like.

See how it works

Your partners in health

Get to know our clinical team. They review our info, prescribe and dispense your treatments.

Dr. Joseph Palumbo

Senior Medical Adviser
Dr-Joseph

Registered with NPI (No. 1043478878)

Meet Joseph  

Dr. Rami Ahmed

Prescribing Clinician
Dr. Rami Ahmed (1)

Registered with NPI (No. 1376740092)

Meet Rami  

Mr Craig Marsh

Clinical Reviewer
Mr-Craig

Registered with GPhC (No. 2070724)

Meet Craig  

Dr Daniel Atkinson

Clinical Reviewer
Dr D,new

Registered with GMC (No. 4624794)

Meet Daniel  

Here’s what you had to say

  • Service reviews
Treated
4.45

Average rating based on 2113 reviews.

Our verification process
551

Very convenient and time saver makes things easier

A
551

Treatment is going great! Fantastic service.

T
551

Understood my needs. Worked very fast. Script showed up quickly. Very satisfied. Highly recommend.

A
551

Ordered 8/21 and arrived 8/24. Always great service.

A
551

All worked as planned.

A
551

Everything is working very well thank you so much

J
See all our reviews 

Read more about Diphenhydramine

Further reading

Woman with pink top and dark hair exercising with boxing gloves on

How to exercise safely when you have asthma

Thankfully, exercising with asthma isn’t impossible. It can take a little bit of planning, but the…

December 19, 2025 Read more
Man wearing checked shirt with glasses and grey beard in garden centre

What is an asthma attack?

Knowing the signs of an asthma attack and what to do is really important if you or someone you know …

December 19, 2025 Read more
A younger woman in a yellow cardigan sits on a couch with an older man in a blue jumper. They're both looking at a book held by the younger woman, and she's pointing to the page

Can taking weight loss injections lower your risk of getting dementia?

Everything you need to know about Wegovy and how it may lower the risk of neurodegenerative diseases…

December 12, 2025 Read more

Give us the inbox treatment.

We're making healthcare more about you. Sign up to our newsletter for personalised health articles that make a difference.

Disclaimer: The information provided on this page is not a substitute for professional medical advice, diagnosis, or treatment. If you have any questions or concerns about your health, please talk to a doctor.

Tell us about a problem

Accept the terms of use terms of use

What did you like about it?

What didn't you like about it?

I'm looking for
Popular searches:
Viagra Wegovy Finasteride Varenicline Zepbound