You should not use  trimethoprim if you have anemia caused by a folate (folic acid) deficiency.
Before taking this medicine
You should not use trimethoprim if you are allergic to it, or if you have:
anemia (low red blood cells) caused by a folate (folic acid) deficiency.
Trimethoprim is not approved for use by anyone younger than 2 months old. Trimethoprim should not be used to treat an ear infection in a child younger than 6 months old.
Tell your doctor if you have ever had:
a folate deficiency;
liver or kidney disease; or
a blood disorder.
Tell your doctor if you are pregnant. Trimethoprim can interfere with your body's ability to metabolize folic acid, a form of vitamin B important in the development of the unborn baby's brain and spinal cord.
It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.
How should I take trimethoprim?
Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.
Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).
Use  trimethoprim for the full prescribed length of time, even if your symptoms quickly improve. Skipping doses can increase your risk of infection that is resistant to medication. This medicine will not treat a viral infection such as the flu or a common cold.
This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are taking trimethoprim.
Store at room temperature away from moisture, heat, and light.
What happens if I miss a dose?
Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include nausea, vomiting, headache, dizziness, confusion, depression, fever, chills, or flu-like symptoms.
Overdose can occur slowly over a long period of time if your daily doses are too high.
