What is high blood pressure? High blood pressure, or hypertension, occurs when the force of blood against the walls of the blood vessels is persistently too high. The upper number records pressure when the heart beats, while the lower number records pressure when the heart rests between beats. According to WHO, hypertension is generally diagnosed when measurements on two different days are 140/90 mmHg or higher. For most people, one reading alone does not confirm the condition; a health professional considers repeat measurements and other health factors. Why is it called a “silent killer”? Most people with hypertension have no symptoms. Feeling well does not mean that your blood pressure is normal. When it is not controlled, hypertension can increase the risk of stroke, heart disease and kidney damage. Measuring blood pressure matters even before symptoms appear. Which signs need urgent care? Very high blood pressure—usually 180/120 mmHg or higher—may occur with a severe headache, chest pain, difficulty breathing, blurred or changed vision, confusion, nausea or vomiting. If a very high reading occurs with symptoms such as these, seek emergency care immediately. Who is at greater risk? Risk rises with age, family history, overweight or obesity, physical inactivity, a high-salt diet, tobacco use, harmful alcohol use, diabetes and kidney disease. Some risk factors cannot be changed, while others can be reduced. What can you do? Measure blood pressure with a suitable device while rested, and repeat the measurement when needed. Keep a record and share it with a health professional. Reducing salt, eating a healthy diet, being physically active, stopping tobacco and reducing or avoiding alcohol can help. Some people also need medication. Do not start, change or stop blood-pressure medicine without advice from a qualified health professional. The key message Symptoms cannot tell you whether you have hypertension. Know your numbers, confirm abnormal readings and obtain an appropriate follow-up plan from a health professional.