A coronary calcium score is a number, ranging from zero to over 1,000, that estimates how much calcified plaque has built up inside the arteries supplying your heart. It comes from a quick, non-invasive CT scan and helps predict your risk of a heart attack in the years ahead. The higher the number, the more plaque is present and the greater the risk.
How the Test Works
The scan itself is straightforward. You lie on a table while a CT scanner takes images of your heart, typically in about 10 minutes. There are no needles, no contrast dye, and no special preparation. The radiation exposure is roughly 1 to 2 millisieverts, which is more than a standard chest X-ray (0.05 mSv) but still considered low.
A computer program then analyzes those images, looking specifically for calcium deposits in the walls of your coronary arteries. Calcium shows up bright white on CT, making it easy to detect and measure. The software calculates what’s known as an Agatston score based on the amount and density of calcium it finds. That single number is your coronary calcium score.
What the Numbers Mean
The score falls into a few broad categories that correspond to increasing levels of heart disease risk:
- Zero: No calcium detected. This suggests a low chance of heart attack in the coming years. It’s the best result you can get, though it doesn’t guarantee zero risk (more on that below).
- 1 to 99: Mild plaque buildup. Some coronary artery disease is present, but the risk is still relatively modest.
- 100 to 300: Moderate plaque deposits. According to the Mayo Clinic, this range carries a relatively high risk of heart attack or other heart disease over the next three to five years.
- Over 300: Extensive plaque. This signals significantly advanced disease and a higher heart attack risk.
Context matters, too. Your score is often compared against other people of the same age and sex. A score of 150 means something different in a 45-year-old than in a 75-year-old, since calcium naturally accumulates with age. If your score lands at or above the 75th percentile for your demographic group, that’s treated as a stronger warning sign regardless of the raw number.
Who Should Get One
This test isn’t recommended for everyone. It’s most useful when your estimated heart disease risk falls into a gray zone, neither clearly low nor clearly high. The 2018 American College of Cardiology and American Heart Association guidelines recommend the scan specifically for risk refinement in people being evaluated for primary prevention of cardiovascular disease. In practice, that means people whose 10-year risk estimate puts them in an intermediate category where the decision to start preventive treatment could go either way.
If your risk is already clearly high (you have diabetes, very high cholesterol, or established heart disease), the scan won’t change your treatment plan. And if your risk is clearly low, the scan is unlikely to reveal anything actionable. The sweet spot is the “should we or shouldn’t we?” group, where a calcium score can tip the scales.
By current guidelines, roughly 13 to 18 percent of men and 3 to 12 percent of women qualify for a scan depending on which risk calculator is used. European guidelines cast a wider net, making nearly half of men and women eligible.
How It Affects Treatment Decisions
One of the most practical uses of a calcium score is deciding whether to start a statin. The 2018 ACC/AHA cholesterol guidelines recommend starting statin therapy if the score is above 100 or at or above the 75th percentile for your age and sex. For someone on the fence about cholesterol medication, this threshold offers a clear, personalized data point.
On the flip side, a score of zero can be genuinely reassuring. For someone with borderline risk factors, it may support holding off on medication and focusing on lifestyle changes instead, with the understanding that the test should be repeated in several years. A zero score doesn’t mean you can ignore risk factors like smoking, high blood pressure, or inactivity. It means your arteries haven’t yet developed the calcified plaque that predicts near-term events.
What the Scan Cannot Detect
This is one of the most important things to understand about the test: it only sees calcified plaque. Coronary artery disease doesn’t start with calcium. Earlier stages involve softer deposits made of fat and fibrous tissue, collectively called noncalcified plaque. These softer plaques are actually the ones most prone to rupturing, which is the event that triggers most heart attacks.
Because the scan relies on calcium to detect disease, it cannot reveal the true total extent of plaque in your arteries. A person with a zero calcium score can still have noncalcified plaque, particularly if they are young or have a strong family history of early heart disease. Research published in Circulation: Cardiovascular Imaging found that relying solely on calcium scoring may miss opportunities for aggressive prevention in high-risk individuals, especially younger men and women whose family members developed heart disease early.
This doesn’t make the test useless. A high calcium score is a reliable predictor of future heart events. But a zero score should be interpreted as encouraging, not as a clean bill of health.
Cost and Insurance Coverage
Here’s the frustrating part: despite guideline endorsements, nearly all insurance payers, including Medicare, deny coverage for coronary calcium scans when used for primary prevention screening. The test is considered elective in most cases, leaving patients to pay out of pocket.
The good news is that many hospitals and imaging centers have lowered their prices to the $50 to $100 range, making it one of the more affordable heart tests available. Some facilities charge more, so it’s worth calling ahead. The American Heart Association has publicly called on insurers to begin covering the scan at reasonable rates, but as of now, that coverage remains the exception rather than the rule.