U.S. doctors online nowAsk doctors free
A 31-year-old member asked:

How many milligrams of antihistamine can a person take at one time?

1 doctor answer2 doctors weighed in
Dr. Thomas Shen
Allergy and Immunology 30 years experience
Unclear: Different antihistamines have different potencies. 10 mg of Zyrtec is equivalent to 180mg of Allegra (fexofenadine). Mg doseage as in all medicines are drug specific. In regard to toxic levels, each has it's own known limit. However too much antihistamine can lead to deadly arrythmias/ Please use the recommended dose.
Last updated Jun 16, 2018


Content on HealthTap (including answers) should not be used for medical advice, diagnosis, or treatment, and interactions on HealthTap do not create a doctor-patient relationship. Never disregard or delay professional medical advice in person because of anything on HealthTap. Call your doctor or 911 if you think you may have a medical emergency.