Side effects of unknown frequency may include: upper respiratory tract infection (e. g. sore throat, inflamed sinuses, common cold), urinary tract infections; increase in certain white blood cells (eosinophilia), deficiency in red blood cells (anaemia), low platelet count (thrombocytopenia); serious allergic reaction (e. g. hypersensitivity, anaphylactic reaction, drug rash); high potassium levels; slow heart rate (bradycardia); upset stomach; eczema (a skin disorder); inflammation of the tendons; kidney impairment including acute kidney failure; weakness; decreased haemoglobin (a blood protein), ineffectiveness of telmisartan.