How quickly does trimethoprim work a high fat meal may delay the time of the effect of this drug. Consult with your doctor before using. Use no more than was prescribed. Take it orally, generally three times daily during (or up to one hour after) each main meal that contains fat. You should take a multivitamin addition including vitamins A, D, E, and K to ensure good supply. The addition should be taken at least two hours before or after you take this medication, such as before going to bed. The recommended dose for adults and children under 12 years is one 120-milligram capsule 3 times daily. Note: this instruction presented here just for review. It’s very necessary to consult with your doctor before using. It helps you to get the best results. Store your medicines at room temperature between 68-77 degrees F (20-25 degrees C) away from light and moisture. Do not store the drugs in the bathroom. Keep all drugs away from reach of children and pets.