A coronary artery calcium (CAC) score is one of the most useful tools available in cardiovascular prevention today — a quick, low-radiation CT scan that can meaningfully change how a person and their physician think about long-term heart disease risk. This guide explains how the test works, how to interpret a result, and where it fits alongside other tools in a prevention strategy.
How the test works
A coronary calcium scan is a non-contrast CT scan of the heart — no IV, no dye, and no need to fast beforehand. The scan itself takes only a few minutes. A specialized algorithm identifies calcium deposits within the walls of the coronary arteries and converts the finding into a single number, the Agatston score, that reflects the total burden of calcified plaque.
Understanding your score
Results are generally grouped into a few broad categories:
A score of zero means no calcified plaque was detected. This is a reassuring finding associated with a low likelihood of a cardiac event in the near term, and it often supports a more conservative, watchful approach to prevention.
A score in the low hundreds reflects mild to moderate calcified plaque and typically prompts a closer look at risk factors and prevention strategy.
A higher score reflects more extensive calcified plaque and usually leads to a more proactive conversation about risk-factor control, and in some cases, additional testing.
The number itself matters less than what it changes about the plan going forward — which is why results are always interpreted in the context of your broader risk profile, not in isolation.
Who is a good candidate for this test
Calcium scoring is most useful for adults, generally in their 40s through mid-70s, who do not have known coronary artery disease and whose traditional risk calculators — which weigh age, blood pressure, cholesterol, smoking history, and diabetes — put them in a borderline or intermediate risk category. In this group, a calcium score can help clarify a decision, such as whether to begin a cholesterol-lowering medication, that isn't obvious from risk factors alone. It is generally less useful for people already known to have coronary disease, those already on preventive therapy for established disease, and those at very low baseline risk.
What the score does not show
A calcium score is a valuable piece of the picture, not the whole picture. It measures calcified plaque specifically — it does not directly capture non-calcified, or "soft," plaque, which can also contribute to risk. It is not a stress test and does not evaluate whether a blockage is causing reduced blood flow. And a score of zero, while reassuring, is not an absolute guarantee, particularly in younger patients with strong risk factors such as heavy smoking, where soft plaque can develop faster than calcification. Most importantly, this test does not replace a clinical evaluation for anyone experiencing symptoms such as chest discomfort, unusual shortness of breath, or palpitations — those symptoms warrant their own workup regardless of a prior calcium score.
How it fits into a broader prevention strategy
Calcium scoring works best as one input among many. Blood pressure, lipid panels, glucose and metabolic health, family history, smoking status, exercise habits, sleep, and body composition all factor into a comprehensive prevention and longevity strategy. The goal is never a single test result — it's a coherent, individualized plan built around your actual risk.
What happens after your results
Your results are reviewed in the context of your full risk profile, not as a standalone number. Depending on the finding, next steps might include lifestyle adjustments, a conversation about preventive medication, or simply continued monitoring on a reasonable timeline. Occasionally, a very high score prompts additional cardiac testing.
Frequently asked questions
Does a calcium score involve radiation?
Yes, but the dose is low — generally comparable to or less than a mammogram, and well below that of a full diagnostic CT scan.
Do I need to prepare for the test?
No special preparation is required beyond avoiding caffeine for a few hours beforehand, since the scan doesn't use contrast dye.
Is a zero score a guarantee I won't have a heart attack?
No test offers a guarantee. A zero score is genuinely reassuring and correlates with a low near-term risk, but ongoing attention to risk factors still matters — particularly for younger patients or those with strong risk factors like smoking.
How often should the test be repeated?
This depends on your individual risk profile and prior result. It is not typically an annual test, and the right interval is best determined with your physician.
If a calcium score or related finding has led to a recommendation you'd like reviewed, a cardiology second opinion can help clarify the evidence and the reasonable options before you decide.