High blood pressure: symptoms, causes and when to see a specialist

High blood pressure is the single largest preventable cause of heart and circulatory disease in Ireland, yet most people who have it feel completely well. In my clinic, many patients tell me their high blood pressure was found by chance, at a GP visit for something else or at a pharmacy check.

This guide explains what the numbers mean, why there are usually no symptoms, what causes high blood pressure, how it affects the kidneys and what you can do to lower it. It also covers when it makes sense to see a specialist. It is general information, so please speak to your GP about your own readings.

What counts as high blood pressure?

Blood pressure is written as two numbers, for example 130/80 mmHg. The first is the pressure when the heart beats and the second is the pressure between beats. The thresholds for high blood pressure (hypertension) depend on where the reading is taken:

• In the clinic: 140/90 mmHg or higher
• At home or on a 24-hour monitor: 135/85 mmHg or higher

Readings at home are usually a little lower than in the clinic, which is why the threshold is lower. For most people, the treatment target is below 140/90 mmHg. Your doctor may set a lower target if you have diabetes, chronic kidney disease or established heart or circulatory disease.

High blood pressure symptoms: why most people feel nothing

The most important thing to know about high blood pressure symptoms is that there usually are none. You can have raised blood pressure for years without any headache, dizziness or other warning sign. This is exactly why it matters: damage to the heart, kidneys, brain and eyes can build up quietly in the background.

Because you cannot rely on how you feel, the only way to know your blood pressure is to measure it. If you have not had it checked recently, ask your GP or pharmacist.

When to seek urgent care

Very high blood pressure can occasionally cause sudden symptoms. Call 112 or 999, or go to an emergency department, if a high reading comes with any of the following:

• chest pain or tightness
• a sudden, severe headache
• breathlessness
• weakness or numbness in the face, arm or leg
• changes in vision or difficulty speaking.

What causes high blood pressure?

In most people, high blood pressure develops gradually and no single cause is found. A number of everyday factors push it up, and several of these can be changed.

Lifestyle factors

• Salt: keeping salt to around 5 to 6 grams a day helps blood pressure, but most people on a typical Irish diet eat well over this
• Alcohol: regular heavy drinking raises blood pressure
• Weight: weight gain raises blood pressure
• Physical activity: too little activity contributes
• Sleep apnoea: loud snoring, daytime sleepiness or pauses in breathing at night can be signs of a condition that raises blood pressure

Medicines that can raise blood pressure

Some medicines and products can push blood pressure up or stop blood pressure tablets from working as well. These include anti-inflammatory painkillers such as ibuprofen and diclofenac, the oral contraceptive pill, steroids, decongestants and certain herbal preparations. If you take any of these regularly, mention it to your GP.

Secondary hypertension

In a minority of people, there is a specific underlying cause. This is called secondary hypertension, and it matters because some causes can be treated directly. They include:

• primary aldosteronism, where the adrenal glands make too much of the hormone aldosterone
• renal artery stenosis, a narrowing of an artery to the kidney
• chronic kidney disease
• obstructive sleep apnoea
• rarer hormonal conditions such as pheochromocytoma and Cushing’s syndrome
• coarctation of the aorta, a narrowing of the main artery from the heart.

High blood pressure and kidney disease

As a nephrologist, I see the link between blood pressure and the kidneys every day. The kidneys help to regulate blood pressure, and high blood pressure is one of the main causes of chronic kidney disease. The relationship works in both directions: damaged kidneys raise blood pressure, and high blood pressure damages the kidneys further.

High blood pressure can also be the first sign of a kidney condition. In polycystic kidney disease, for example, it is often the earliest feature. This is why a simple blood test for kidney function and a urine test for protein (see ACR vs PCR) are part of the routine assessment of anyone with high blood pressure.

Checking your blood pressure at home

Home blood pressure monitoring gives a more realistic picture than a single clinic reading. Some people have what is called white coat effect: their blood pressure is high in the clinic but normal at home. Your GP may also arrange a 24-hour ambulatory monitor, which records your blood pressure throughout the day and night and gives the most complete picture.

To get reliable home readings:

1. Use a validated upper-arm monitor with the right cuff size.
2. Sit quietly for a few minutes with your back supported and your arm resting at heart level.
3. Take two readings a minute or so apart, morning and evening, over several days.
4. Write down every reading and bring the record to your next appointment.

How to lower blood pressure

Lifestyle changes help everyone with high blood pressure, whether or not they also take medication. The most effective steps are:

• cutting down on salt, including the salt hidden in bread, processed meats and ready meals
• following a DASH-style diet, rich in fruit, vegetables, whole grains and low-fat dairy
• reaching and keeping a healthy weight
• regular physical activity
• keeping alcohol within recommended limits
• getting any sleep apnoea assessed and treated.

Many people also need medication. Common choices include ACE inhibitors, angiotensin receptor blockers (ARBs), calcium channel blockers and thiazide-type diuretics, often in combination. For most people, high blood pressure is a long-term condition, and treatment is long-term too. Please do not stop your tablets because your readings look good: normal readings usually mean the treatment is working.

When to see a specialist about high blood pressure

Most high blood pressure is well managed by GPs. Specialist assessment adds value in particular situations, including:

• blood pressure that stays high despite three or more medications, known as resistant hypertension
• a suspected underlying cause, such as primary aldosteronism or renal artery stenosis
• high blood pressure diagnosed under the age of 40
• high blood pressure alongside chronic kidney disease
• high blood pressure during or after pregnancy
• signs that blood pressure is affecting the heart, kidneys, brain or eyes.

A specialist assessment looks for an underlying cause and checks for effects on other organs. Depending on your situation, it may include 24-hour ambulatory monitoring, blood and urine tests for kidney function, electrolytes and hormones, a kidney ultrasound and a heart scan. You can read more about how I assess and treat patients on my hypertension page.

How to arrange an appointment

I see patients by GP referral, so the first step is to talk to your GP. Your GP can find referral details on the information for referring GPs page, and the patient information page explains what to bring and what to expect on the day. If you are unsure whether a referral is right for you, my guide to when to see a kidney specialist may help.

I hold clinics at Blackrock Clinic, The Beacon Hospital, Bon Secours Dublin, the Hermitage Medical Centre and St Vincent’s Private Hospital. You can find addresses and directions on the locations page.