Can you take a double dose of Allegra?
Short answer
Medication question
No — taking a double dose of Allegra is not recommended. Doubling up does not improve allergy symptom relief and simply increases the amount of drug in your system without benefit. If you missed a dose, skip it and resume your normal schedule. For an accidental overdose, contact Poison Control at 1-800-222-1222.
This is a general research summary, not medical advice. A pharmacist can confirm it for your situation.
Key facts
Poison Control (US): 1-800-222-1222. Available 24/7 for accidental ingestion guidance.
The approved adult dose of fexofenadine for allergic rhinitis is 60 mg twice daily or 180 mg once daily.
In overdose studies, dizziness, drowsiness, and dry mouth were the most common effects observed.
Here's the nuance
A one-liner rarely tells the whole story. This is the honest detail behind the short answer above.
Allegra (fexofenadine) works by blocking histamine H1 receptors in a dose-dependent way up to the therapeutic dose — once those receptors are adequately blocked, taking more doesn't provide additional relief. The 180 mg once-daily dose is calibrated to provide effective, sustained antihistamine coverage. Taking two doses at once simply doubles the amount of drug circulating in your body without meaningfully increasing the therapeutic effect.
There are two common scenarios that lead people to consider a double dose: trying to make up for a missed dose, or believing a higher dose will work better or faster. In both cases, the answer is the same — don't. If you missed a dose and your next dose is coming up soon, skip the missed one. If you're finding that standard doses aren't adequately controlling your symptoms, that's a conversation for your pharmacist or allergist, not a reason to self-increase the dose.
Fexofenadine has a relatively good safety margin compared to older antihistamines, but that doesn't mean it is harmless in excess. In studies of supratherapeutic doses, side effects including dizziness and drowsiness were observed more frequently. Very large overdoses should be treated seriously.
If someone has accidentally taken a double dose or more — especially a child — call Poison Control immediately at 1-800-222-1222 (US). They can advise whether monitoring at home or a medical visit is appropriate. In an emergency, call 911.
The key points
The handful of things that decide the answer — skim these if you only read one section.
More is not better for antihistamines
Once H1 receptors are adequately blocked at the therapeutic dose, additional fexofenadine doesn't provide more relief. The standard dose is calibrated for effectiveness.
For missed doses: skip, don't double
The correct response to a missed dose that's almost due is to skip it and resume your regular schedule with the next scheduled dose.
Increased side effects with excess
Supratherapeutic doses in studies produced increased side effects including dizziness and drowsiness. Allegra is not risk-free in large amounts.
Children need extra caution
Accidental double dosing in children should prompt a call to Poison Control (1-800-222-1222) even if the child appears fine. Do not wait for symptoms.
Poor symptom control = talk to your allergist
If one dose isn't enough to control your allergy symptoms, speak with your doctor or allergist. There may be a better treatment approach, including allergy immunotherapy.
Please read before acting on this
General information — not medical advice
This page is a general research summary about the medication in question. It does not account for your specific health, other medicines you take, or your dose, and it can go out of date. It is not medical advice, a prescription, or a substitute for professional judgment.
Ask your pharmacist or prescriber before starting, stopping, changing, or continuing any medication — they can check it against your situation in minutes.
❓Frequently Asked Questions
For most adults, accidentally taking two standard 180 mg doses (360 mg total) is unlikely to cause a serious emergency, but it is still not recommended. You may experience increased side effects such as dizziness, headache, or drowsiness. Call Poison Control (1-800-222-1222) to describe what happened and get guidance on whether you need to be seen medically. Don't try to induce vomiting unless told to do so.
No. Doubling your Allegra dose is not an appropriate treatment for a severe allergy attack. Allegra (fexofenadine) is a maintenance antihistamine, not an acute-treatment drug. For a severe allergic reaction (anaphylaxis, severe breathing difficulty, throat swelling), call 911. For worsening seasonal allergy symptoms, speak with your doctor or allergist about adjusting your treatment plan.
This should only be done under a doctor's direction. The approved adult dose is 60 mg twice daily or 180 mg once daily. Doses above this have been studied in clinical settings but are not standard self-directed practice. If you feel your current dose is inadequate, consult your prescriber rather than adjusting on your own.
Reviewed by
Dr. Chet TharpeMD
Last reviewed July 2026
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This content is for general informational purposes only. It is not medical advice, a prescription, or a substitute for professional judgment, and it does not account for your health, other medications, or dose. Always ask your pharmacist or prescriber before starting, stopping, or changing any medication.