Help! I Accidentally Took Two Zyrtec

Our pharmacist answers our latest question regarding an individual who accidentally took an extra dose of their morning Zyrtec (cetirizine).


I hope you can help me as I'm quite nervous. I usually take my Zyrtec dose at night, after dinner. However, tonight, later in the evening, I completely forgot I had taken my dose and took another one hour later. Am I going to be okay?

Asked by Madeline On Jul 08, 2021

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Jul 08, 2021
Last updated Mar 03, 2022

Key points

  • The FDA-approved maximum daily dose of Zyrtec (cetirizine) is 10mg
  • However, many clinical studies have concluded that higher doses of Zyrtec (up to 20mg, or two tablets) are associated with only mild side effects and can provide better symptom relief than 10mg
  • Experiencing major side effects from taking two tablets of Zyrtec (20mg total) would be very uncommon. More likely, you will only experience mild side effects, such as sleepiness and dry mouth

Hello and thank you for your question!

I certainly understand your worry regarding accidentally taking an extra dose of Zyrtec!

The good news is that although you may experience some side effects (more on this below), Zyrtec (cetirizine) is an antihistamine that is considered relatively safe, and it would take fairly high doses to present a real medical emergency for most individuals. Accidentally taking one extra pill, in most situations, is nothing to be too concerned about.

Before moving on to the next section, I always like to put in these articles the information for Poison Control. It is a valuable resource to refer to in situations where accidental ingestion of a substance (including extra doses of medication) has occurred. It provides great direction on when you should seek emergency care and what symptoms to look out for.

You can go to their website,, or call them at 1-800-222-1222.

Zyrtec Safety At High Doses

Zyrtec is a second-generation antihistamine that is available over the counter (it was at one time prescription only). Other second-generation antihistamines include Claritin (loratadine) and Allegra (fexofenadine).

For adults, the recommended dosage is 10mg (one Zyrtec tablet) every 24 hours. This is the FDA-approved maximum daily dose.

In the situation you described in your question, you took one extra pill, which would equate to 20mg. Even though this is higher than the daily recommend dose, it wouldn't be considered toxic in the vast majority of situations.

In fact, several clinical studies have been published where high doses of Zyrtec have been utilized, with minimal side effects.

One such study, published in 2013 in the Journal of Dermatological Treatment, concluded that a double dose of Zyrtec (cetirizine), which is 20mg (the dose you took), was effective in helping to reduce the symptoms of itching that was previously not responding to lower doses:

Conclusion: Doubling the dose of cetirizine may be efficacious to the patients with urticaria refractory to the regular dose of cetirizine.

This study only noted mild side effects to this dose.

Several other studies have come to the same conclusion...that 20mg of Zyrtec is actually helpful for a lot of individuals who haven't had great success with conventional doses.

In terms of how much Zyrtec would be considered a dangerous overdose, the prescribing information for the drug (which is found on the FDA website) specifically discusses situations where high doses have been consumed.

It mentions two cases of overdose, one where an adult took 150mg (15 tablets) and another where a child took 180mg (18 tablets). Only mild side effects were reported at these high doses. Per the prescribing information:

In one adult patient who took 150 mg of ZYRTEC, the patient was somnolent [sleepy ]but did not display any other clinical signs or abnormal blood chemistry or hematology results. In an 18 month old pediatric patient who took an 12 overdose of ZYRTEC (approximately 180 mg), restlessness and irritability were observed initially; this was followed by drowsiness.

So, based on the available information we have regarding Zyrtec, you shouldn't be too worried about that extra dose you took as it is fairly well tolerated, even at higher than recommended doses.

Zyrtec Side Effects

Like most drugs, the side effects of Zyrtec are dose dependent, meaning that higher doses tend to increase the risk of side effects occurring.

The side effects of Zyrtec (and all antihistamines) include:

  • Sleepiness
  • Fatigue
  • Dry mouth
  • Dizziness
  • Headache
  • Diarrhea
  • Nausea

The most common side effect is sleepiness (often referred to as somnolence). That is what you are most at risk for with taking an extra dose, but it should wear off as the dose wears off, within 24 hours.

Past that, again, you shouldn't have too much trouble.

Final Words

I want to add the caveat here that everyone's medical situation is different. Even though taking an extra dose of Zyrtec won't cause too many issues for most people, some may be more at risk for others.

One such example would be with individuals who have heart conditions.

High doses of antihistamines can cause changes in heart rhythm. Two tablets of Zyrtec probably won't put you much more at risk of an adverse effect happening, but is still something to keep in mind. If you do experience any troubling symptoms, I highly recommend contacting Poison Control (information at the top of this answer) or going to your nearest emergency room.

I hope this answer helps you!

Thanks so much for reaching out.


  • Dose-ranging comparative evaluation of cetirizine in patients with seasonal allergic rhinitis, PubMed
  • Zyrtec Prescribing Informaton, AccessFDA
  • Double dose of cetirizine hydrochloride is effective for patients with urticaria resistant: a prospective, randomized, non-blinded, comparative clinical study and assessment of quality of life, PubMed
  • Efficacy and safety of cetirizine therapy in perennial allergic rhinitis, PubMed

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 11 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication related questions!

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