High blood pressure in children is more common than most parents realize, affecting roughly 2% to 5% of kids and teens in the United States. The causes range from everyday factors like weight and diet to underlying medical conditions involving the kidneys, heart, or hormone-producing glands. What’s driving a child’s elevated readings depends a lot on their age: younger children are more likely to have an identifiable medical cause, while teenagers more often develop high blood pressure linked to weight and lifestyle, similar to adults.
Primary vs. Secondary Hypertension
Pediatric high blood pressure falls into two broad categories. Primary hypertension means there’s no single identifiable disease behind it. It tends to show up in older, heavier children and adolescents and is now the more common form overall. Secondary hypertension means another condition is pushing blood pressure up. Children with secondary hypertension tend to be younger and often have a lower body weight than those with primary hypertension, which is one reason doctors pay close attention when a young, lean child has high readings.
Kidney Problems Are the Leading Medical Cause
When a specific disease is responsible, kidney issues top the list. The kidneys regulate how much fluid and salt stay in the bloodstream, so any condition that damages or disrupts them can raise blood pressure. In children, the most common kidney-related causes include being born with a single kidney, structural abnormalities of the kidneys or urinary tract, undersized kidneys, polycystic kidney disease, and narrowing of the arteries that supply blood to the kidneys (renal artery stenosis).
These conditions may be present from birth but go unnoticed for years. A kidney ultrasound is one of the most useful screening tools when doctors suspect secondary hypertension. In one study, kidney ultrasound had the highest diagnostic yield of any test, identifying structural problems in over a third of children evaluated for secondary causes.
Heart and Blood Vessel Defects
A structural heart defect called coarctation of the aorta is another well-known cause. In this condition, a section of the body’s main artery is abnormally narrow, which forces the heart to pump harder to push blood past the blockage. The result is high blood pressure in the arms and upper body, with noticeably lower pressure and weaker pulses in the legs. In older children and teens, the main sign is often persistently elevated blood pressure in the arms. Over time, the extra workload thickens the heart muscle, which can cause problems if the defect isn’t corrected.
Weight and Sodium Intake
Excess weight is the single biggest driver of primary hypertension in children and teens. Carrying extra body fat changes how the body handles salt, insulin, and stress hormones, all of which push blood pressure upward. This creates a situation where salt sensitivity becomes amplified. Research on obese adolescents has shown that their blood pressure responds more dramatically to changes in sodium intake than it does in normal-weight peers, likely because of higher insulin levels and increased activity in the body’s “fight or flight” nervous system.
A large national study of U.S. children and adolescents found that for every additional 1,000 milligrams of sodium consumed per day, systolic blood pressure rose by about 1 point on average. That effect was roughly seven times larger in kids who were overweight or obese, with a 1.5-point increase per 1,000 milligrams. The two risk factors, weight and sodium, appear to amplify each other rather than simply adding together. Children in the study consumed anywhere from about 1,300 to over 8,000 milligrams of sodium daily, with much of the high end coming from processed and fast foods.
Hormonal and Endocrine Disorders
Several hormone-related conditions can cause high blood pressure in children, though they’re relatively rare. These involve glands that overproduce hormones affecting blood vessel tightness, fluid retention, or heart rate.
- Cushing syndrome: The body produces too much cortisol, a stress hormone. In children over five, this is most often caused by a small, benign tumor in the pituitary gland. The excess cortisol raises blood pressure, causes weight gain (particularly in the face and midsection), and can slow growth.
- Congenital adrenal hyperplasia: Certain genetic forms of this condition cause the adrenal glands to produce excess hormones that retain salt and water, raising blood pressure even in young children.
- Thyroid overactivity: An overactive thyroid speeds up the heart and increases the force of each heartbeat, which can elevate blood pressure readings.
- Adrenal tumors: Tumors on the adrenal glands can flood the body with adrenaline-like chemicals (catecholamines) or with aldosterone, a hormone that tells the kidneys to hold onto sodium. Either scenario raises blood pressure, sometimes dramatically.
These conditions often come with other noticeable symptoms, such as unusual weight changes, growth problems, or episodes of rapid heartbeat and flushing, which help doctors distinguish them from primary hypertension.
ADHD Medications and Other Drugs
Stimulant medications used to treat ADHD are among the most common drug-related causes of elevated blood pressure in children. Medications like methylphenidate and amphetamine-based drugs activate the same part of the nervous system that raises heart rate and constricts blood vessels. A systematic review of 14 clinical trials found that both types of stimulants produced modest but statistically significant increases in systolic blood pressure. Community-based data from one large study showed average increases of about 3 points in both systolic and diastolic pressure among children taking stimulants.
For most children, a 3-point bump is clinically minor. But for a child whose blood pressure is already on the higher end, it can tip readings into an elevated range. Other medications that can raise blood pressure include oral steroids (used for asthma flares or autoimmune conditions) and certain over-the-counter decongestants.
Sleep Apnea
Obstructive sleep apnea, where the airway repeatedly collapses during sleep, is an underappreciated contributor to childhood hypertension. A National Institutes of Health study linked sleep apnea in children to an increased risk of high blood pressure during the teen years. The mechanism isn’t fully understood, but the repeated drops in oxygen during sleep appear to trigger inflammation, stress on blood vessel walls, and changes in the nervous system’s regulation of blood pressure. Obesity drives much of the overlap between sleep apnea and hypertension, but sleep apnea also contributes to elevated blood pressure independently of weight.
Signs that a child might have sleep apnea include loud snoring, gasping or pausing during sleep, restless sleep, mouth breathing, and daytime sleepiness or behavioral problems. Enlarged tonsils and adenoids are the most common cause in children who aren’t overweight.
How High Blood Pressure Is Defined in Kids
Blood pressure in children isn’t measured against a single number the way it is in adults. Instead, a child’s reading is compared to other children of the same age, sex, and height. The American Academy of Pediatrics recommends annual blood pressure checks starting at age 3 for healthy children. Kids under 3 should be screened if they have risk factors like premature birth, kidney disease, or a heart defect.
The classification system uses percentiles:
- Elevated (prehypertension): Readings between the 90th and 95th percentile for age, sex, and height, or any reading above 120/80 even if it falls below the 90th percentile.
- Stage 1 hypertension: Readings from the 95th percentile up to the 99th percentile plus 5 mmHg.
- Stage 2 hypertension: Readings above the 99th percentile plus 5 mmHg, which warrants prompt evaluation.
A single high reading doesn’t mean a child has hypertension. Diagnosis requires elevated readings on at least three separate occasions, since anxiety, activity, and even the size of the blood pressure cuff can throw off results. When blood pressure is consistently high, doctors typically start by looking at weight, family history, and kidney function before considering less common causes. The younger the child and the higher the readings, the more likely it is that a specific underlying condition is responsible.