High blood pressure, also called hypertension, is a condition most often associated with adults. But kids can have high blood pressure too, even as infants.

High Blood Pressure in Kids

An estimated 3% of kids have high blood pressure. In babies, it's usually caused by prematurity or problems with the kidneys or heart. While hypertension is far more common among adults, the rate among kids is on the rise, a trend that experts link to the increase in childhood obesity.

Many kids and teens with high blood pressure have no other health problems but do have a family history of hypertension and an unhealthy lifestyle — a bad diet, excess weight, stress, and insufficient physical activity.

If it goes untreated, high blood pressure can eventually lead to damage to the heart, brain, kidneys, and eyes. But if it's caught early, monitored, and treated, a child with high blood pressure can lead an active, normal life.

Understanding Blood Pressure

Blood pressure is the pressure the blood exerts against the blood vessel walls as the heart pumps. The pressure increases when the heart contracts and pushes blood into the vessels and lowers when the heart relaxes, but there's always a certain amount of pressure in the arteries.

Blood pressure is driven by two physical forces — the one from the heart as it pumps blood into the arteries and through the circulatory system, and the other from the arteries as they resist this blood flow.

Blood pressure changes from minute to minute and is affected by activity and rest, body temperature, diet, emotional state, posture, and medications.

Long-Term Consequences of High Blood Pressure

When someone has high blood pressure, the heart and arteries have a much heavier workload. The heart must pump harder and the arteries are under greater strain as they carry blood. If high blood pressure continues for a long time, the heart and arteries may no longer work as well as they should. Other organs that are receiving the blood, like the kidneys and brain, may also be affected.

Having high blood pressure puts someone at a higher risk for stroke, heart attack, kidney failure, loss of vision, and atherosclerosis (hardening of the arteries).

While high blood pressure doesn't always cause symptoms, it still affects the body and puts a person at risk for those long-term health problems. In rare cases, severe hypertension can cause headaches, visual changes, dizziness, nosebleeds, heart palpitations, and nausea.

If your child has severe high blood pressure and has any of these symptoms, seek medical care immediately.

Measuring Blood Pressure

Doctors measure blood pressure with a sphygmomanometer, which has a cuff that's wrapped around the upper arm and pumped up to create pressure. When the cuff is inflated, it compresses a large artery in the arm, stopping the blood flow for a moment. Blood pressure is measured as air is gradually let out of the cuff, which allows blood to flow through the artery again.

The doctor or nurse will also put a stethoscope over an artery to hear the first pulse as the blood flows through — this is the systolic pressure (or the pressure at the peak of each heartbeat). The diastolic pressure (the pressure when the heart is resting between beats) is noted when the sounds disappear.

When a blood pressure reading is taken, the higher number represents the systolic pressure and the lower number represents the diastolic pressure. For example: 120/80 (120 over 80) means that the systolic pressure is 120 and the diastolic pressure is 80.

Blood pressure also can be measured by automated devices, which are good for screening, but a manual blood pressure is more accurate.

As kids grow, their blood pressure increases from a systolic pressure of about 70-90 in an infant to adult values in a teenager. Among young kids, the "normal" range will depend on gender, age, and height; your doctor will be able to compare your child's blood pressure with national norms.

In kids, high blood pressure is defined as a blood pressure greater than the 95th percentile for their age, height, and gender (in other words, 95% of kids of the same age, height, and gender will have blood pressure below this number).

It's not unusual for a first blood pressure reading to be high because a child is nervous, so the doctor will likely take three readings and use an average of the three to determine whether your child has high blood pressure or is at risk for developing it.

Some doctors use a test called ambulatory blood pressure monitoring in which a child wears a blood pressure cuff all day. Some consider it more accurate than blood pressure tests in the doctor's office because the child is less likely to be affected by any stress from the doctor visit.

Causes of High Blood Pressure

The causes of high blood pressure differ, depending on the age of the child. The younger the child, the more likely the high blood pressure is linked to some other illness.

High blood pressure among infants most commonly occurs in those born prematurely. Some newborns have high blood pressure because of problems with the kidneys (most commonly), lungs, heart, or vascular system. Often, these problems are due to bronchopulmonary dysplasia, an immaturity of the lungs in premature babies, or problems like coarctation of the aorta, a narrowing of part of the major blood vessel that transports blood away from the heart.

Among school-age kids and teens, hypertension is usually linked to excess weight. In some cases it's due to a problem with the kidneys, although other conditions — like abnormalities in the blood vessels and hormonal disorders — can also be responsible.

Some medications (such as steroids or oral contraceptives) can lead to high blood pressure, as can overconsumption of alcohol and illegal drugs.

Diagnosing High Blood Pressure

Because high blood pressure usually doesn't produce any symptoms, diagnosing the condition in kids can be tricky. Blood pressure varies a lot from day to day so several blood pressure checkups are often necessary to make the diagnosis (unless the pressure is very high when treatment is needed promptly).

The only way to know whether a child has high blood pressure is to get it checked regularly. It's often helpful to get blood pressure readings away from the doctor’s office, like at school or at home if there is a blood pressure monitoring device available. These readings should always be done when resting.

Doctors usually start measuring blood pressure during routine checkups when kids are 3 years old. So it's important not to miss these appointments, particularly if your child is obese or if there's a family history of high blood pressure.

Treating High Blood Pressure

If an underlying illness is causing hypertension, treating that illness may be enough to get the blood pressure back to normal. If there's no underlying illness, the doctor may recommend weight loss, increased intake of fruits and vegetables, decreased salt intake, increased exercise, and even relaxation techniques.

Kids with hypertension also should quit or never start smoking, which can worsen the long-term associated heart problems.

Most doctors prefer not to prescribe medication for kids with mild hypertension. However, in cases in which lifestyle changes do not bring improvement, medications may be necessary.

Exercise and participation in organized sports is encouraged for all patients with hypertension. In fact, staying fit is the key to both weight and blood pressure control. Only in the unusual situation when hypertension is very severe would exercise be restricted, and then it should be resumed after control with medications.

If your child is overweight, an ongoing weight-loss program monitored by your doctor and a minimum of 30 minutes of aerobic exercise every day may be recommended.

But kids with severe hypertension should not participate in weight- or power-lifting, bodybuilding, or strength training until their blood pressure is under control and a doctor OK's it.

Although rare in kids, mild to moderate hypertension over time can cause damage to the heart, kidneys, and blood vessels. Diagnosing and treating high blood pressure will help prevent this damage.

Reviewed by: Samuel S. Gidding, MD
Date reviewed: April 2011