A CT calcium score test is a type of computed tomography (CT) scan that takes detailed images of the heart. Used with an electrocardiogram (ECG), it assesses the amount of calcium in the coronary arteries.
The coronary arteries are the blood vessels that transport oxygen and nutrient-rich blood to the heart. Higher than normal levels of calcium in these arteries can indicate a buildup of hardened plaques of fatty substances, including cholesterol, and a medical condition called atherosclerosis. Atherosclerosis may lead to a narrowing of the blood vessels and blockages where the blood struggles to flow. It can also progress into coronary artery disease and, if left undiagnosed, may eventually lead to a heart attack and increase your risk of strokes.
What is a Calcium Score Test?
A calcium score test (also called a coronary artery calcium, or CAC score) shows the level of calcium deposits, or calcification, in the arteries that supply the heart with blood, oxygen and nutrients.
Calcium deposits are an indicator of atherosclerosis, or fatty plaque buildup, which is ultimately an indicator of the risk of coronary artery disease and consequently, the risk of a heart attack and strokes. The higher the CAC score, the higher the risk. Calcium scoring is carried out as a CT scan alongside an ECG.
Why You Might Need a Calcium Score Test
Coronary artery calcium scoring allows doctors to assess your risk of heart disease, and there are various reasons why you may need this kind of test:
Assess Risk of Coronary Artery Disease
There are certain risk factors and medical conditions that can mean that you have a higher risk of developing heart disease or having a heart attack. These include high blood pressure, high cholesterol, obesity and having a family history of coronary artery disease. Health care practitioners use a CT calcium score test to assess your risk of heart disease and strokes and, if necessary, suggest treatments and lifestyle changes that can reduce your risk.
Evaluate Chest Pain of Unknown Cause
Chest pain can be caused by heart disease or calcification in the arteries that supply blood and nutrients to the heart. However, chest pain can also be caused by digestive problems, pulled muscles and other reasons. Calcium scores can therefore be useful in determining the exact cause. A low CAC score may suggest that your chest pain is being caused by something other than heart problems.
Strong Family History of Heart Disease
If heart disease runs in your family, you may be regularly monitored to check the health of your heart and blood vessels. These checks will include coronary artery calcium scoring tests.
High Cholesterol
Cholesterol is a type of fat that’s carried by the blood vessels. If your levels are high, due to genetics or a high fat diet, it becomes a risk factor for coronary artery disease.
High Blood Pressure
Similarly to high cholesterol, high blood pressure can also put you at a higher risk of heart disease as it can damage the blood vessels, leaving them more susceptible to blockages and plaque buildup.
Diabetes
Type 2 diabetes causes higher than normal levels of sugar in the blood. Over time, high blood sugar levels can damage the lining of the blood vessels, which can leave them at a higher risk of plaque formation and atherosclerosis, leading to coronary artery disease.
Being Overweight
Carrying excess weight and being obese can increase fatty plaque buildup in the arteries that supply the heart, a risk factor for coronary artery disease. If you’re overweight, you’re also more at risk of developing high cholesterol and high blood pressure.
History of Smoking
Smoking causes damage to the lining of the blood vessels, which can then cause them to narrow, meaning reduced blood and oxygen flow to the heart; another risk factor for heart disease and strokes.
Who Does Not Need a Test
If you’ve already been diagnosed with heart disease, you’re at a high risk of coronary artery disease or you have symptoms of heart disease, you’re unlikely to benefit from a cardiac CT for calcium scoring test. A calcium score test is best suited to those who have risk factors for heart disease and haven’t yet had a diagnosis.
Similarly, a calcium score test isn’t recommended for those with no risk factors for coronary artery disease.
What a Calcium Score Test Can Diagnose
A cardiac CT for calcium scoring test is a relatively routine test that your doctor may use to look for calcification, which can be an indicator of the following medical conditions:
Atherosclerosis
Atherosclerosis is the “furring up” or blocking of arteries due to high levels of fats and cholesterol in the blood, causing a buildup of fatty plaque deposits and potential narrowing and blockages.
Plaque Buildup in Arteries
See above, Atherosclerosis.
Coronary Artery Disease
Coronary artery disease is a medical condition caused by atherosclerosis and a buildup of fatty plaque deposits in the coronary arteries, leading to blockages and interruptions to the blood supply to the heart.
Coronary Artery Calcification
Coronary artery calcification describes the buildup of calcium deposits in the coronary arteries, causing them to harden and develop atherosclerosis.
Cardiovascular Disease Risk
Cardiovascular disease describes the medical conditions that affect the heart and the blood vessels, including calcification and atherosclerosis. A cardiac CT for calcium scoring test will assess your risk of developing cardiovascular disease in the future, which could eventually lead to a heart attack.
Risk of Heart Attack
A CT calcium score test is very useful in determining your risk of having a heart attack caused by calcification and atherosclerosis, which block the blood supply to the heart muscle.
Asymptomatic Heart Disease
Asymptomatic heart disease refers to heart disease with no noticeable symptoms, such as chest pains. However, if you have risk factors, such as obesity, high blood pressure, high cholesterol or a strong family history of heart disease, you may be at risk of heart disease, even with no other symptoms. A CT calcium score test is therefore beneficial for detecting calcification and atherosclerosis, which may mean your risk of a heart attack is increasing.
Need for Statin Therapy
Statins are medications that lower levels of cholesterol in the blood, in turn decreasing your risk of heart attacks and strokes. If a calcium score test results in a high calcium score, your doctor may recommend that you start taking a daily statin to manage your cholesterol levels.
Severity of Artery Narrowing
Calcium deposits, or calcification, are a good indicator of atherosclerosis, or fatty plaque buildup, that can cause a narrowing of the arteries that supply the heart with oxygen and nutrient-rich blood. The higher the level of calcification, or CAC score, the more severe the artery narrowing is likely to be. The narrower the arteries, the less blood can reach the heart muscle, reducing the oxygen and nutrient supply, which can result in a heart attack.
How a Calcium Score CT Works
A CT for calcium scoring test works in the same way as a standard CT scan on any other body part. It uses x-rays to take detailed images of the inside of the body. Unlike regular x-ray scans, a CT scan takes cross-sectional images that are then collated to create three-dimensional images that can be used to assess the health of the whole organ.
At the same time as the CT scan, an ECG machine records electrical activity from the heart to time the CT images with your heartbeat to give a clearer picture of the level of calcification.
Equipment Used
A CT scanner is a large, doughnut-shaped machine fitted around a flat medical bed that slides in and out of the CT scanner. An ECG machine uses electrodes stuck to the chest to measure electrical activity within the heart.
Benefits
Coronary artery calcium scoring is quick, painless and effective. It’s most beneficial for those with risk factors for heart disease, such as high blood pressure and high cholesterol, and are yet to have a diagnosis of heart disease.
Risks & Side Effects
There are no known side effects to calcium scoring tests. However, there are some risks. CT scans use x-rays to produce detailed images of the heart and blood vessels. X-rays expose patients to a small amount of radiation, about the same amount of radiation you'd normally be exposed to from the environment in a year.
The more CT scans you have, the more radiation you’re exposed to. Repeated radiation can lead to a small risk of developing cancer later in life. However, this risk is usually outweighed by the benefit of calcium scoring and heart disease risk assessment.
CT scans aren’t recommended for pregnant women due to the risk of x-rays to an unborn child.
Limitations
Tomography CT for calcium scoring tests look specifically for calcium deposits, rather than narrowing or damage to the arteries that supply the heart.
How to Prepare
Unlike CT scans on other body parts, a CT calcium score test requires changes to your diet and lifestyle beforehand. The advice may change, depending on your symptoms and medical history, so it’s important to follow the individual advice given by your doctor. However, on the whole, you’ll be asked to avoid eating, drinking (including alcohol and caffeine) and using nicotine and tobacco products in the hours leading up to your test.
The Procedure Explained: What to Expect
A calcium score CT scan is usually carried out in the radiology department of a hospital or a dedicated scanning clinic by a radiologist. There might be small differences between medical settings, but generally, calcium score tests are carried out as follows:
Changing into a Gown
To ensure you’re comfortable throughout, you’ll be asked to change into a medical gown for the procedure. This also ensures that you’re not wearing anything that contains metal that cannot be worn inside a CT scanner.
Removal of Metal Objects
Metallic objects interfere with the x-rays used during CT scanning, distorting the final images. Therefore, all clothing, including underwear, must be removed. Jewellery, hair clips and watches must also be removed, and phones, bank cards, cash and keys must be left in a secure place outside the scanning room.
Lying on the CT Table
Once you’ve changed into a gown, you’ll be asked to lie down on your back on the medical table that moves in and out of the CT scanner. Your radiologist will help to ensure you’re in the correct position.
Placement of ECG Leads
Your radiologist will place three sticky pads that contain electrodes onto your chest and attach the ECG leads to these pads. They’ll clean the area with medical wipes beforehand to ensure they stick properly, and if necessary, they’ll shave small areas to ensure proper placement of the pads. Your medical gown will cover your chest area once the pads and leads are in place.
Instructions on Breath-Holding
There may be certain points during your scan when you’ll need to hold your breath for 10 to 20 seconds. Your radiologist will explain this to you and will let you know when you’ll need to hold your breath.
CT Scanner Takes Images
To avoid repeated radiation exposure, your radiologist will control the CT scanner remotely, either from a different room or from behind a screen in the same room. You’ll be able to see them through a glass window, and talk to them throughout.
Once you’re ready, they’ll begin the scanning process to take detailed images of the heart and the heart’s arteries and veins from different positions, while you remain still.
What Happens After a Calcium Score Test?
When your radiologist is happy they have the right images, the scan will be over. The actual scan itself will take around 10 to 15 minutes, but you can expect your whole appointment to be around 40 minutes. You’ll be able to get dressed and return home when your scan is finished.
Getting the Results
Your radiographer will send the detailed images taken during your CT calcium score test to a specialist doctor called a radiologist. They will assess your results and discuss them with your referring doctor and a cardiologist. You’ll normally receive your results within a few days.
Costs
In the UK, a private calcium score test starts at around £400. Consultations and any subsequent treatment will cost extra.
Get a Calcium Score Test CT
Having a family history of heart attacks or being told that you’re at a high risk of coronary artery disease is understandably frightening. A CT calcium score test can put your mind at ease by helping you start making diet and lifestyle changes or taking medications that can help reduce your risk.
It may take some time to get an appointment with an NHS doctor who can refer you for a calcium scoring test. If you’re concerned, book an appointment for a private heart scan with us as a first step.
FAQs
How Often Should You Have a Calcium Score Test?
It can be helpful to have a CT for calcium scoring every three to five years.
How Reliable Is a Calcium Score Test?
CT calcium score tests are considered very reliable, however, they may be carried out in conjunction with other tests and scans to assess overall heart and blood vessel health.
What Is a Calcium Score Blood Test?
A blood test for calcium will only show how much calcium is in the blood. A CT calcium score test looks specifically at the level of calcium deposits in the coronary arteries and is a better indicator of heart disease risk.
References
Radiological Society of North America (RSNA) and American College of Radiology (ACR). (n.d.-b). Cardiac CT for calcium scoring. Radiologyinfo.org. https://www.radiologyinfo.org/en/info/ct_calscoring
Professional, C. C. M. (2025g, April 23). Calcium score test. Cleveland Clinic. https://my.clevelandclinic.org/health/diagnostics/16824-calcium-score-screening-heart-scan
CT calcium scoring (or cardiac calcium scoring) | Nuffield Health. (n.d.). https://www.nuffieldhealth.com/tests-scans/ct-calcium-scoring-or-cardiac-calcium-scoring
Heart problems | Royal Brompton & Harefield hospitals. (n.d.). https://www.rbht.nhs.uk/our-services/heart-problems
Website, N. (2024e, November 27). Coronary heart disease. nhs.uk. https://www.nhs.uk/conditions/coronary-heart-disease/