The standard maximum for adults is one 180 mg Allegra tablet once a day, or one 60 mg tablet twice a day. Both options deliver the same total of 120 to 180 mg of the active ingredient (fexofenadine) in 24 hours, and you should not exceed that amount without medical guidance.
Adult Dosing by Formulation
Allegra comes in two common strengths for adults and children 12 and older. Which one you have on your shelf determines how many tablets you take:
- Allegra 24-Hour (180 mg): One tablet once a day. That single tablet covers a full 24 hours.
- Allegra 12-Hour (60 mg): One tablet every 12 hours, for a maximum of two tablets per day.
These two regimens are considered equivalent. Clinical testing shows that both maintain allergy relief through the end of their dosing window. The drug starts working within about an hour, peaks at two to three hours, and a single 60 mg dose still has measurable antihistamine activity at the 12-hour mark. The 180 mg dose maintains its effect through a full 24-hour period.
Children’s Dosing
Children’s Allegra uses lower doses and typically comes as a liquid suspension. For kids aged 2 to under 12, the dose is 30 mg (one teaspoon or 5 mL of the liquid) every 12 hours, with a maximum of two doses (60 mg total) in 24 hours. Children 6 to 11 can also use 30 mg chewable or dissolvable tablets on the same twice-daily schedule.
Once a child turns 12, they follow the adult dosing guidelines.
What Happens If You Take Too Much
Fexofenadine has a wide safety margin compared to older antihistamines. It stays out of the brain for the most part, which is why it rarely causes drowsiness at normal doses. But taking more than the recommended amount can cause dizziness, rapid heartbeat, headache, drowsiness, or agitation. Poison control guidelines for children flag any acute intake over three times the maximum daily dose as needing medical evaluation.
The drug has an average half-life of about 14.4 hours, meaning it clears slowly. Doubling up because you forgot a dose or feel your allergies breaking through won’t make it work better and just increases your chance of side effects.
Kidney Function Changes the Dose
Your kidneys handle much of the work clearing fexofenadine from your body. If you have reduced kidney function, the recommended starting dose drops to 60 mg once a day rather than twice daily. The same applies to children with kidney issues: their doses are halved. If you know you have kidney disease, this is worth discussing with your pharmacist or doctor before defaulting to the label instructions.
Fruit Juice Reduces Absorption
This is one of Allegra’s quirks that catches people off guard. Orange juice, apple juice, and grapefruit juice all interfere with proteins that help your body absorb fexofenadine. The result is that less of the drug gets into your bloodstream, and it may not control your symptoms as well. The FDA specifically notes this interaction, and the Allegra label says not to take it with fruit juices.
The fix is simple: take Allegra with water. If you drink juice with breakfast, take your dose at a different time or wait a while before having juice.
Antacids Need a Two-Hour Gap
Antacids containing aluminum or magnesium (common in many heartburn products) also reduce how much fexofenadine your body absorbs. If you use both, take your Allegra at least two hours before the antacid. Taking them at the same time can meaningfully blunt Allegra’s effectiveness, leaving you wondering why your allergy medicine isn’t working.
Choosing Between Once and Twice Daily
If you’re deciding between the 180 mg and 60 mg versions, consider your routine. The once-daily 180 mg tablet is more convenient and eliminates the risk of forgetting a second dose. The 60 mg twice-daily option gives you slightly more flexibility, since you can skip the evening dose on days when your symptoms are mild. Both are equally effective for seasonal allergies. For chronic hives, the FDA-approved dosing specifically calls for 60 mg twice daily, so the 12-hour formulation may be more appropriate in that case.