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Diagnosis - Stroke

Strokes are usually diagnosed by doing physical tests and studying images of the brain produced during a scan.

When you first arrive at hospital with a suspected stroke, the doctor will want to find out as much as they can about your symptoms.

A number of tests can be done to confirm the diagnosis and determine the cause of the stroke.

These may include: 

  • a blood test to find out your cholesterol and blood sugar level
  • checking your pulse for an irregular heartbeat
  • taking a blood pressure measurement

Brain scans

Even if the physical symptoms of a stroke are obvious, brain scans should also be done to determine:

  • if the stroke has been caused by a blocked artery (ischaemic stroke) or burst blood vessel (haemorrhagic stroke)
  • which part of the brain has been affected
  • how severe the stroke is

Everyone with suspected stroke should have a brain scan within 1 hour of arriving at hospital if possible.

An early brain scan is especially important for people who:

  • might benefit from medicine to clear blood clots (thrombolysis), such as alteplase or early anticoagulant treatment
  • are already taking anticoagulant treatments
  • have a lower level of consciousness

This is why a stroke is a medical emergency and you should call 999 when a stroke is suspected – there's no time to wait for a GP appointment.

The 2 main types of scans used to assess the brain in people who have had a suspected stroke are:

CT scans

A CT scan is like an X-ray, but uses multiple images to build up a more detailed 3-dimensional picture of your brain to help your doctor identify any problem areas.

During the scan, you may be given an injection of a special dye into one of the veins in your arm to help improve the clarity of the CT image and look at the blood vessels that supply the brain.

If a stroke is suspected, a CT scan is usually able to show whether you have had an ischaemic stroke or a haemorrhagic stroke.

It's generally quicker than an MRI scan and can mean you're able to receive appropriate treatment sooner.

MRI scans

An MRI scan uses a strong magnetic field and radio waves to produce a detailed picture of the inside of your body.

It's usually used in people with complex symptoms, where the extent or location of the damage is unknown. 

It's also used in people who have recovered from a transient ischaemic attack (TIA)

An MRI scan shows brain tissue in greater detail, allowing smaller, or more unusually located, areas affected by a stroke to be identified.

As with a CT scan, special dye can be used to improve MRI scan images.

Swallow tests

A swallow test is essential for anybody who has had a stroke, as the ability to swallow is often affected soon after having a stroke.

When a person cannot swallow properly, there's a risk that food and drink may get into the windpipe and lungs, which can lead to chest infections such as pneumonia. This is called aspiration.

The test is simple. The person is given a few teaspoons of water to drink. If they can swallow this without choking and coughing, they'll be asked to swallow half a glass of water.

If they have any difficulty swallowing, they'll be referred to a speech and language therapist for a more detailed assessment.

They usually will not be allowed to eat or drink normally until they have seen the therapist.

Fluids or nutrients may need to be given directly into a vein in the arm (intravenously) or through a tube that's inserted through the nose and down into the stomach.

Heart and blood vessel tests

Further tests on the heart and blood vessels might be done later to confirm what caused your stroke.

Carotid ultrasound

A carotid ultrasound scan can help to show if there's narrowing or blockages in the neck arteries leading to your brain.

An ultrasound scan involves using a small probe (transducer) to send high-frequency sound waves into your body.

When these sound waves bounce back, they can be used to create an image of the inside of your body.

When carotid ultrasonography is needed, it should happen within 48 hours.


An echocardiogram makes images of your heart to check for any problems that could be related to your stroke.

This usually involves moving an ultrasound probe across your chest (transthoracic echocardiogram).

An alternative type of echocardiogram called transoesophageal echocardiography (TOE) may sometimes be used.

An ultrasound probe is passed down your gullet (oesophagus), usually under sedation.

As this allows the probe to be placed directly behind the heart, it produces a clear image of blood clots and other abnormalities that may not be seen with a transthoracic echocardiogram.

Page last reviewed: 13 September 2022
Next review due: 13 September 2025