This is an overview of 10 common causes of high blood pressure. But, let’s start with a definition.
What is High Blood Pressure?
High blood pressure, or hypertension, is a common condition where the long-term force of the blood against your artery walls is consistently too high. It forces your heart to work harder to pump blood throughout the body.
Structurally, this chronic pressure can damage the delicate inner lining of your blood vessels, leading to a narrowing and hardening of the arteries over time (atherosclerosis).
Because it rarely causes obvious symptoms in its early stages, it is frequently referred to as a “silent killer,” quietly increasing the risk of serious cardiovascular complications.
What it is
The most common form of high blood pressure, developing gradually over many years with no single, identifiable medical cause. It is typically driven by a combination of genetic predisposition, natural aging, and lifestyle factors like a high-salt diet, physical inactivity, and chronic stress.
Common signs
Usually completely silent. It is typically discovered incidentally during routine medical checkups or blood pressure screenings, rather than through noticeable physical symptoms.
When to Worry
Your home readings consistently remain above 140/90 mmHg despite making positive lifestyle changes
You begin to experience frequent, dull headaches or occasional bouts of mild dizziness
You have a strong family history of early heart disease or stroke and have never had your pressure checked
When to See a Doctor
Routinely. Book an appointment with your GP surgery or practice nurse to establish an accurate baseline and discuss a long-term management plan.
What it is
A secondary cause of hypertension where damaged kidneys lose their ability to effectively filter waste and excess fluid from the blood. This fluid retention increases blood volume, while the kidneys simultaneously release excess amounts of a hormone called renin, which constricts the blood vessels.
Common signs
Fluid retention causing puffiness around the eyes or swelling in the ankles and feet. Changes in urination frequency, fatigue, and persistent high readings that resist standard treatments are also common.
When to Worry
You notice a sudden, significant decrease in your urine output or visible blood in your urine
Swelling in your legs or ankles becomes severe and leaves a lasting indentation when pressed (pitting edema)
Your blood pressure spikes sharply alongside new-onset, unexplained shortness of breath
When to See a Doctor
Soon. A doctor will need to arrange blood and urine tests to evaluate your kidney function and select blood pressure medications that specifically protect the kidneys.
What it is
A sleep disorder where the airway repeatedly collapses during sleep, momentarily stopping breathing. These frequent drops in blood oxygen levels trigger sudden surges in the sympathetic nervous system, releasing stress hormones that constrict blood vessels and spike blood pressure, even during the daytime.
Common signs
Loud, disruptive snoring interrupted by gasping or choking sounds during the night. Severe daytime fatigue, waking up with a dry mouth, and morning headaches are classic indicators.
When to Worry
Your partner notices you completely stop breathing for several seconds multiple times during sleep
You experience extreme daytime sleepiness that causes you to nod off while driving or operating machinery
Your high blood pressure remains stubbornly high despite taking three or more different medications
When to See a Doctor
Soon. Your GP can refer you for a sleep study to confirm OSA, as treating the airway collapse with a CPAP machine often significantly lowers blood pressure.
What it is
Endocrine conditions caused by hormone-producing abnormalities in the adrenal glands. This includes Conn’s syndrome (excess aldosterone causing salt retention), Cushing’s syndrome (excess cortisol disrupting fluid balance), and phaeochromocytoma—a rare tumor of the adrenal medulla that releases massive surges of adrenaline and noradrenaline, causing volatile, severe spikes in blood pressure.
Common signs
Persistent or highly volatile hypertension. Conn’s and Cushing’s often cause muscle weakness, fluid retention, or distinct abdominal weight gain.
A phaeochromocytoma typically presents with abrupt, terrifying “spells” characterized by a pounding heartbeat, severe headaches, and profuse sweating.
When to Worry
You experience sudden, unpredictable episodes of extreme palpitations, sweating, and anxiety alongside a dramatic spike in blood pressure
You experience frequent, painful muscle spasms or severe muscle weakness that interferes with your mobility
You develop hypertension at a remarkably young age (under 30) without any obvious risk factors
When to See a Doctor
Soon. Specialist evaluation by an Consultant Endocrinologist is necessary to run specific blood or 24-hour urine tests (such as metanephrines) and discuss targeted medication or surgical options.
What it is
The narrowing of one or both of the main arteries that supply blood to your kidneys, usually due to a buildup of fatty plaques. Because the kidneys perceive the reduced blood flow as a sign of low overall blood pressure, they mistakenly trigger a powerful hormonal cascade that forces the body’s blood pressure to skyrocket.
Common signs
A sudden, severe elevation in blood pressure that appears out of nowhere, or a previously stable reading that suddenly becomes unmanageable.
When to Worry
Your blood pressure jumps to dangerously high levels unexpectedly after the age of 55
A doctor detects a whistling sound (bruit) when listening to your abdomen with a stethoscope
Your kidney function drops significantly immediately after starting a standard blood pressure medication like an ACE inhibitor or ARB
When to See a Doctor
Promptly. An urgent referral to a Consultant Nephrologist for a CT or MR angiogram of the renal arteries is required to assess the narrowing and discuss potential specialist interventions.
What it is
Hypertension triggered or worsened by the regular use of specific over-the-counter medications, prescription drugs, or recreational substances.
Common culprits include steroids (e.g. prednisolone), non-steroidal anti-inflammatory drugs (NSAIDs like ibuprofen), oral contraceptive pills (OCPs), HRT, decongestants, and excessive alcohol consumption.
Common signs
A noticeable, steady rise in your home blood pressure readings that corresponds directly with the introduction or increased use of a particular medication or substance.
When to Worry
This is always a scenario that requires prompt attention. Continuing to take these substances can counteract your prescribed antihypertensive therapies, leading to volatile or dangerously high spikes.
You notice your blood pressure spiking daily after taking over-the-counter cold remedies or painkillers
When to See a Doctor
Soon. Speak to your GP or pharmacist to review your current medications and find safer alternatives that will not compromise your cardiovascular health.
What it is
A temporary spike in blood pressure that occurs specifically within clinical environments, such as a doctor’s surgery or hospital clinic. It is triggered by the natural, often subconscious anxiety or stress of being examined by a medical professional.
Common signs
Blood pressure readings that are consistently high or borderline when measured at the clinic, but perfectly normal and healthy when checked at home or via a 24-hour ambulatory monitor.
When to Worry
The stress of attending appointments causes you severe anxiety or palpitations
Your clinic readings are used to prescribe medications, but your home readings suggest your pressure is actually running too low, causing dizziness
You have never verified your home monitor against a validated device to ensure the readings are accurate
When to See a Doctor
Routinely. Share a diary of your home readings with your GP to prevent unnecessary over-medication and ensure your treatment is based on your true everyday averages.
What it is
A critical, sudden spike in blood pressure where the readings climb to an extreme level—typically defined as a systolic pressure over 180 mmHg or a diastolic pressure over 120 mmHg. This extreme force poses an immediate threat of acute organ damage.
Common signs
Can present as an asymptomatic spike, but frequently causes severe, sudden symptoms due to the immense pressure strain on the brain, heart, and blood vessels.
When to Worry
This is always a critical situation. An extreme spike can quickly lead to a stroke, heart attack, or acute heart failure if the pressure is not lowered safely.
Your reading is 180/120 mmHg or higher and is accompanied by a severe headache, chest pain, blurry vision, or shortness of breath
You experience sudden confusion, difficulty speaking, or weakness on one side of your body
When to See a Doctor
Urgently. Call 999 or go to the nearest A&E department immediately. Do not wait to see if the pressure drops on its own; it requires immediate assessment and intravenous medication.
What it is
High blood pressure conditions that develop specifically during pregnancy, typically after the 20th week. This ranges from gestational hypertension (isolated high blood pressure) to preeclampsia, a serious condition where hypertension is accompanied by signs of system-wide damage, most often impacting the kidneys and liver.
Common signs
New-onset elevations in blood pressure during the second or third trimester. Preeclampsia is distinguished by rapid swelling in the hands and face, persistent headaches, visual changes, and excess protein detected in urine tests.
When to Worry
This is always a scenario that requires prompt attention. If left unmanaged, pregnancy-induced hypertension can rapidly progress, leading to life-threatening complications for both the mother and baby.
You develop sudden, severe swelling in your face, around your eyes, or in your hands
You experience changes in your eyesight, such as flashing lights, spots, or temporary blurring
You experience a severe, unremitting pain just below your ribs on the right side
Urgently. Contact your midwife, or go to your maternity unit (or straight to A&E) immediately for emergency assessment and close foetal and maternal monitoring.
What it is
Structural abnormalities of the heart and its primary artery. This includes coarctation of the aorta (a congenital narrowing of the main artery leaving the heart) and aortic regurgitation (a leaking aortic valve that causes blood to flow backward into the heart), both of which force the heart to pump with significantly greater pressure to maintain systemic blood flow.
Common signs
High blood pressure that may exhibit stark discrepancies, such as being significantly higher in the arms than the legs (common in coarctation). Aortic regurgitation often presents with a remarkably wide pulse pressure (a very high top number and very low bottom number) and a bounding pulse.
When to Worry
You experience sudden, severe cramping, weakness, or fatigue in your legs during mild physical exertion
You experience an awareness of a strong, pounding heartbeat (palpitations) accompanied by sudden breathlessness or chest tightness
You suffer from chronic, unexplained nosebleeds or dizzy spells alongside elevated blood pressure readings
When to See a Doctor
Routinely for an initial cardiac workup and echocardiogram if structural abnormalities are suspected. Urgently if you develop sudden chest pain, severe shortness of breath, or fainting spells.
A single high reading is not a diagnosis. Blood pressure fluctuates constantly throughout the day due to stress, caffeine, and physical exertion. A diagnosis of hypertension requires a pattern of consistently elevated readings taken over days or weeks, ideally confirmed by a home blood pressure diary or a 24-hour ambulatory monitor.
Home monitoring must be done correctly. To get an accurate reading, always sit quietly for 5 minutes before checking. Keep your feet flat on the floor, support your arm at heart level, and use a validated upper-arm cuff monitor rather than a wrist device. Avoid smoking, exercise, or caffeine for at least 30 minutes beforehand.
Lifestyle modifications are foundational therapies. Whether or not you require prescription medication, reducing your dietary salt intake, maintaining a healthy weight, exercising regularly, and limiting alcohol are powerful tools that significantly lower blood pressure and reduce your overall cardiovascular risk.
Hypertension is managed routinely every day. GPs, practice nurses, and pharmacists are experts at managing high blood pressure. Never stop taking your prescribed antihypertensive medications abruptly without consulting your doctor, as doing so can cause a dangerous rebound spike in pressure.
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