It is safe to take 20mg of Zyrtec (cetirizine) daily? I take it in the morning but 12 hrs later I am suffering. If I don't take another one at night I dont sleep.

No. Max recommended dose is 10mg/24 hrs why do you need Zyrtec (cetirizine) at all? We propose to treat the cause of allergy so that you don't need to depend on medicine. Please visit us to learn the causes of allergy and how we propose to treat the cause and also Please give us your feedback .