Older patients may be more prone to side effects when they have a history of hyperkalemia while using TRIMETHOPRIM. Please inform your doctor if you are undergoing dialysis treatment since TRIMETHOPRIM is moderately removed by haemodialysis. Your doctor may schedule the dosage after dialysis. Please undergo an examination to rule out CDAD's chances if you experience diarrhoea following TRIMETHOPRIM therapy. Let your doctor know if you are undergoing any vaccinations with live bacterial vaccines (like typhoid vaccine) since TRIMETHOPRIM may affect vaccines' activity. TRIMETHOPRIM may induce photosensitivity and makes your skin more sensitive to the sun; hence wear sunscreen when you step out. Please seek medical advice if you are pregnant or breastfeeding before taking TRIMETHOPRIM.

Drug-Drug Interaction: TRIMETHOPRIM may interact with anticoagulants (warfarin, heparin), anti-cancer drugs (methotrexate), anti-diabetics (repaglinide), heart-related drugs (procainamide, digoxin), anti-malarial drugs (pyrimethamine and dapsone), fits medicine (phenytoin), antibiotics (rifampicin), fluid retention drugs (spironolactone, amiloride), blood pressure medicines, and potassium supplements.

Drug-Food Interaction: Avoid alcohol consumption while taking TRIMETHOPRIM to prevent unpleasant side-effects.

Drug-Disease Interaction: Before taking TRIMETHOPRIM, let your doctor know if have any anaemia, kidney or liver diseases, diabetes, vitamin deficiency (folate or folic acid), blood disorders like bone marrow suppression and G6PD deficiency, hyperkalaemia or low levels of sodium in the blood, porphyria, and muscle weakness.

• Include more fibre enriched food in your diet, as it can be easily digested by your gut bacteria, which helps stimulate their growth. Thus, fibre foods may help restore healthy gut bacteria after a course of antibiotics. Whole grains like whole-grain bread, brown rice should be included in your diet.
• Eating grapefruit during antibiotics treatment can prevent the body from utilizing TRIMETHOPRIM properly. So, avoid intake of grapefruit or grapefruit juice with the antibiotic.
• Avoid intake of alcoholic beverages with TRIMETHOPRIM as it can make you dehydrated and affect your sleep. This can make more challenging for your body to aid the TRIMETHOPRIM in fighting off infections.
• Manage stress, eat healthily, drink plenty of water, exercise regularly, and get plenty of sleep.
• Do not walk barefoot at places like gym showers to prevent bacterial infections.

• Renal, hepatic, and blood function tests are advised during prolonged therapy to rule out any toxicity caused due to overdose of TRIMETHOPRIM. 
• Clostridium difficile associated diarrhoea (CDAD) is reported during usage of antibiotics like Trimethoprim. Please see your doctor if you experience prolonged diarrhoea.
• Monitor your blood sugar levels regularly since TRIMETHOPRIM may affect your blood glucose levels if you have diabetes.
• Trimethoprim is moderately removed during dialysis, hence let your doctor know if you are undergoing dialysis treatment so that the dose can be scheduled after the dialysis.