A calcium score test is a quick, noninvasive CT scan of your heart that takes about 5 minutes on the table. The scan detects tiny deposits of calcium in the walls of your coronary arteries, which signal the buildup of plaque. Here’s what happens before, during, and after the test.
How to Prepare
Preparation is minimal. You’ll be asked to avoid caffeine and smoking for a few hours before the test. There’s no fasting required and no IV contrast dye involved, which makes this simpler than many other heart imaging tests. When you arrive, you’ll likely change into a medical gown and remove any jewelry around your neck or chest, since metal can interfere with the images.
What Happens During the Scan
A technologist places small adhesive patches (electrodes) on your chest and connects them to an electrocardiogram, which tracks your heartbeat throughout the scan. This is the key to getting clear pictures: the scanner uses your heart’s electrical signal to time each image to the brief moment between beats when the heart is relaxed and nearly still. Without that synchronization, the images would be blurry from the constant motion of a beating heart.
You lie on your back on a narrow table that slides into a doughnut-shaped CT scanner. The ring around you rotates and takes multiple cross-sectional images of your chest in seconds. You’ll be asked to hold your breath once or twice for about 10 seconds each time so that your lungs stay still and don’t obscure the view. The actual scanning takes roughly 5 minutes, though the full appointment, including check-in and paperwork, runs about 30 minutes.
There are no needles, no injections, and no recovery time. You can drive yourself home and resume normal activities immediately.
Radiation Exposure
The scan does use X-rays, but the dose is relatively low. A typical calcium score scan delivers about 2 to 3 millisieverts (mSv) of radiation, though it can range from less than 1 to about 10 mSv depending on the protocol and equipment used. For comparison, you absorb roughly 3 mSv per year just from natural background radiation. It’s significantly less than a full cardiac CT angiogram, which is one reason the calcium score test is used as a first-line screening tool.
How the Score Is Calculated
A computer analyzes the images and assigns a number called the Agatston score, which reflects the total amount of calcium detected across all your coronary arteries. The score is based on both the area and the density of each calcium deposit. Your results typically come back within a few days, sometimes sooner.
Here’s what the numbers mean:
- 0: No detectable calcium. This is associated with a low risk of heart attack over the next several years, even in people with some traditional risk factors like high cholesterol.
- 1 to 99: Mild plaque buildup. Even small amounts (scores of 1 to 10) can be significant in younger adults, where any calcium is unusual.
- 100 to 399: Moderate plaque buildup. At this level, guidelines recommend starting preventive treatment such as cholesterol-lowering medication if it hasn’t been initiated already.
- 400 and above: Extensive plaque. The likelihood of a significant narrowing in at least one coronary artery is greater than 90%, particularly in people who already have other risk factors.
Your score is also compared against a database of people your age and sex, so you’ll often see a percentile ranking alongside the raw number. Someone with a score of 50 might be at the 90th percentile for their age group, meaning more calcium than 90% of similar people, which shifts the clinical picture even though the raw number looks modest.
Who Should Get One
The test is most useful for people in a gray zone of heart disease risk. Current guidelines focus on adults whose estimated 10-year risk of a cardiovascular event falls between 5% and 20%, a range where the decision to start preventive medication could go either way. In that group, nearly half have a calcium score of zero, which can be reassuring enough to hold off on medication. About 18% score 100 or above, which tips the balance toward treatment.
A score of zero even shows up in about a third of people estimated to be at high risk (above 20% on standard calculators), which is why the scan can meaningfully change a treatment plan in either direction. It’s not recommended as a routine screening for low-risk adults or for people who already have confirmed heart disease.
Cost and Insurance
The test typically costs between $100 and $400 out of pocket, with some clinics offering it on the lower end. Most private insurance plans and Medicare treat it as an elective screening test and don’t cover it. Medicare Part B will cover CT scans ordered to evaluate a specific medical concern, but if your scan is classified as screening, you’ll likely pay the full amount. It’s worth calling your insurance and the imaging center ahead of time to confirm pricing, since the cost varies widely by location.