The time taken by Meritol 25mg Tablet XL to start working varies from person to person. Usually, Meritol 25mg Tablet XL starts working within 15 minutes. However, in some patients, it may take up to 2 hours to start working. It starts acting slowly and the maximum or full effect is usually experienced within a span of 1 week. In case you do not feel any difference while taking Meritol 25mg Tablet XL, do not panic. The medicine exerts its beneficial effects when taken for a long time.