High blood pressure, or hypertension, most commonly occurs without any symptoms and has for this reason been referred to as the "silent killer." Uncomplicated hypertension can persist for years, even decades, without causing symptoms. However, when complications of the condition begin to develop due to damage to the vascular system, symptoms can occur. Symptoms of complicated hypertension (high blood pressure) can include dizziness, shortness of breath, headache, and blurred vision. Other possible symptoms are nosebleeds, blood in the urine, fatigue, chest pain, and a pounding sensation in the neck, chest, or ears.

Severe high blood pressure is referred to as malignant hypertension, in which the diastolic ("bottom") blood pressure reading is over 140 mmHg. Malignant hypertension is a medical emergency and can cause stroke. Symptoms can include nausea, severe headache, blurred vision, and dizziness. Some people with malignant hypertension may develop kidney failure. They may experience a decrease in urine output and swelling (edema), most pronounced in the lower legs.

Source: http://www.rxlist.com