Hypertensive emergencies are usually accompanied by a number of unsettling body changes, such as difficulty speaking, says the AHA.
Other warning signs include chest pain, shortness of breath, back pain, numbness/weakness, change in vision.
The AHA says people should not wait to see if their pressure comes down on its own if they are experiencing these symptoms, but to call the emergency services immediately.
In the long-term, lifestyle changes will be required to stabilise your blood pressure reading.
There are two key components to blood pressure control – diet and exercise.
In relation to the former, you should cut down on the amount of salt in your food and eat plenty of fruit and vegetables.
Salt disrupts the sodium balance in your body, which can cause your blood pressure to rise.
According to the NHS, you should aim to eat less than six (0.2oz) of salt a day, which is about a teaspoonful.
Eating dark, leafy green vegetables can offset the harmful effects of salt intake because they are a rich source of magnesium.
“Magnesium helps to maintain a healthy blood pressure, so eating a balanced, colourful diet is a must,” says Holland and Barrett.
Eating a healthy, balanced diet can also aid weight loss, which is crucial to controlling high blood pressure.
“Being overweight forces your heart to work harder to pump blood around your body, which can raise your blood pressure,” warns the NHS.