Telmisartan can cause a range of side effects, from minor symptoms to major problems that will require the intervention of medical personnel. The milder adverse reactions that could be experienced are nasal congestion, runny nose, abdominal pain, diarrhea, tiredness, sweating, sore throat, cough, back pain, headaches, weakness, or dizziness. The following more serious reactions should be reported immediately to the patient's physician: urination problems, difficult breathing, swelling of the extremities, chest pain, or a feeling that the patient may faint.