High blood pressure or white coat hypertension?

What is white coat hypertension?

Hypertension is the medical term for high blood pressure, and ‘white coat’ refers to a doctor’s white coat, and therefore a clinical or medical environment. Simply put, white coat hypertension means having a high reading only when your blood pressure is measured away from your normal home environment, usually in a clinic or surgery.

Most people with consistently high readings (140/90mmHg or above) do have high blood pressure but there are a few who will have white coat hypertension. People with white coat hypertension have high readings (140/90mmHg or above) only when they have their blood pressure measured at their doctors surgery or in a clinic, and have normal blood pressure readings outside a clinic environment. A small number of people may have white coat hypertension that goes unrecognised which could mean being wrongly diagnosed as having high blood pressure and receiving unnecessary treatment.

What causes white coat hypertension?

Blood pressure goes up and down throughout the day and night in everyone, which is normal. For example, when you are excited or in pain, when you have just exercised or when you are angry your blood pressure rises; when you are asleep or resting then your blood pressure falls.

White coat hypertension and the white coat effect are caused by anxiety, when your body stimulates your ‘fight or flight’ response. Many people are aware that they feel nervous or anxious, but many others may think that they are relaxed when, in fact, they are not. It can affect anyone, young or old, male or female and some people find that anxiety can raise their blood pressure by as much as 30mmHg on the systolic (top) number. Being relaxed, in a quiet environment and being given reassurance can help to reduce this effect.

How do I know if I have white coat hypertension?

There are no symptoms of white coat hypertension, you won’t feel unwell if you have it. The only way to find out if you are affected is to have your blood pressure measured outside your doctor’s surgery or clinic. There are two ways of doing this- Taking readings yourself at home and or Ambulatory Blood Pressure Measurement (ABPM) - sometimes also called 24-hour monitoring

A few people will be asked to have ABPM, which is a test to see what your blood pressure is like over a period of 24-hours. A small portable monitor takes readings regularly and automatically over a day and a night. Your doctor can then look at an average of the daytime readings and this should show whether you have a normal blood pressure at home. If the average reading is 135/85mmHg or less then it is normal. Some doctor’s surgeries now have ABPM equipment or alternatively you may need to go to your local hospital outpatients department to have the machine fitted. .

You may also be asked to use an automatic or a semi-automatic blood pressure machine to take a series of readings yourself at home. Some doctors and clinics will lend you a monitor, usually for two weeks, and ask you to take readings at certain times of the day. After you have taken these readings your doctor or nurse will analyse them and work out an average. You can also buy a blood pressure monitor to use at home, to monitor your blood pressure levels.

Will I need to be treated if I have white coat hypertension?

Doctors believe that if you have white coat hypertension you are at less risk of heart disease or stroke than someone who has sustained high blood pressure, but at a greater risk than someone who has normal blood pressure at all times. For this reason it is important to make sure that you have your blood pressure checked regularly – at least once a year. This is to make sure that if your blood pressure does start to rise, you can take steps to lower it as soon as possible.

Many people with white coat hypertension go on to develop high blood pressure in the future. For this reason, particularly if you have other risk factors like smoking, or high cholesterol, your doctor may advise you to start treatment.

You can help to prevent a rise in blood pressure by following a healthy lifestyle. This means eating a diet low in fat and salt and high in fruit and vegetables, being active and the right weight for your height and not drinking alcohol excessively. You can also buy a blood pressure monitor to use at home, to monitor your blood pressure levels. See the information sheet ‘Measuring your blood pressure at home’.

I have been diagnosed with high blood pressure, could it be white coat hypertension?

A small number of people that are diagnosed with high blood pressure may have white coat hypertension. If you have ‘mildly’ raised blood pressure, ie, up to 160/99mmHg, then white coat hypertension could account for this level of blood pressure. Above 160/99mmHg it is likely that even if you took into account a rise in blood pressure because of anxiety, it would still be high. For example, if you had a systolic reading of 180mmHg in the surgery and took into account a possible white coat effect of 30mmHg then it means your systolic reading would be 150mmHg, which is still a high reading.

If your high blood pressure has been diagnosed from a small number of readings (unless the blood pressure is very high) then it is possible that white coat hypertension could be a factor. A diagnosis of high blood pressure should be made after a series of readings, over a period of time, to take into account the possibility of white coat hypertension.

Finding out whether you may have white coat hypertension is important as it can make the difference between being treated, or not, and can affect other aspects of your life such as insurance and work. If you are concerned, talk to your doctor or nurse.