Question 1

How long does it take for cetirizine to start working?

Accepted Answer

Cetirizine typically begins to relieve symptoms within 1 hour of taking a tablet.

Question 2

How long does the effect of cetirizine last?

Accepted Answer

The antihistamine effect lasts 24 hours, so one dose covers a full day.

Question 3

How long does cetirizine stay in your system?

Accepted Answer

The elimination half-life is 8–11 hours. It takes about 2–3 days for cetirizine to be completely cleared from the body.

Question 4

Does food affect how fast cetirizine works?

Accepted Answer

Food may slightly delay absorption (peak time may increase by about 1 hour), but it does not reduce the overall effect. You can take it with or without meals.

Question 5

When is the best time to take cetirizine?

Accepted Answer

Take it at the same time each day. For once-daily dosing, evening is often preferred if you experience drowsiness, but cetirizine is usually non-sedating.