Hypertension, or high blood pressure, is often called the 'silent killer' because it usually has no symptoms, yet can lead to serious problems like heart attack, stroke, and kidney damage. Your blood pressure reading is expressed as two numbers, one over the other. If the top number is 140 or greater, or the bottom number is 90 or greater, you're said to have high blood pressure. The higher these numbers, the more serious your risk. In most cases, doctors don't know what causes hypertension, but it can often be controlled by maintaining a normal weight. If you're overweight, losing a few pounds may allow you to keep your blood pressure down without the need for medication. Exercise is another important strategy because it can help with both weight loss and blood pressure reduction. Even a modest weight loss can improve your blood pressure. Conversely, gaining weight may cause your blood pressure to rise. Since many people with high blood pressure are unaware of their condition, it's wise to have yours checked on a regular basis.