An Agatston score is a number that represents the total amount of calcium buildup in your coronary arteries, measured by a quick CT scan of your heart. The score starts at zero (no visible calcium) and has no upper limit, though anything above 300 signals extensive buildup and a meaningfully higher risk of heart attack. Doctors use it as one of the clearest tools available for gauging how much plaque has accumulated in the arteries that feed your heart.
How the Score Is Measured
The test itself is a non-contrast CT scan, meaning no dye is injected into your veins. You lie on a table, hold your breath for a few seconds, and the scanner captures images of your heart timed to your heartbeat. The whole process takes about 10 minutes. Radiation exposure is low, roughly 1 to 2 millisieverts, which is a fraction of the 10 millisieverts you’d get from a standard chest CT.
The software then identifies every speck of calcium in your coronary arteries. For each deposit, it measures two things: the physical area of the calcium and how dense it is. Density is graded on a 1-to-4 scale based on how bright the calcium appears on the scan. Each deposit’s area is multiplied by its density factor, and all the individual scores are added together. That total is your Agatston score.
What the Numbers Mean
Scores fall into four widely used categories:
- 0: No visible calcium. Very low risk of coronary artery disease.
- 1 to 99: Mild calcium deposits. Mildly increased risk.
- 100 to 299: Moderate plaque deposits. Moderately increased risk.
- 300 or higher: Extensive calcification. Moderate to severely increased risk of a cardiac event.
These categories give a broad picture, but context matters. A score of 85 in a 45-year-old is far more concerning than the same score in a 75-year-old, because some calcium accumulation is expected with age. That’s why many cardiologists also look at your percentile ranking, which compares your score to other people of the same age, sex, and race. The MESA (Multi-Ethnic Study of Atherosclerosis) calculator is the standard tool for this comparison and is referenced in current prevention guidelines.
The Significance of a Zero Score
A score of zero is sometimes called the “power of zero” in cardiology because it carries strong reassurance. In people without symptoms, a zero score is associated with a very low rate of cardiovascular events over 15 years of follow-up. Even in people who do have symptoms like chest pain, research shows that only 1 to 2 percent of those with a zero score turn out to have significant blockages, and their long-term outlook remains good.
That said, a zero score doesn’t guarantee clean arteries. Coronary plaque comes in two forms: hard, calcified deposits that the scan picks up, and softer, non-calcified plaque that it cannot see. A person can have fatty buildup in their artery walls with no calcium present at all. This is why doctors treat the score as one piece of the puzzle rather than the final word, especially if you’re already experiencing symptoms.
How Doctors Use the Score for Treatment Decisions
The Agatston score is most useful for people in a gray zone of heart disease risk, where standard factors like cholesterol, blood pressure, and family history don’t clearly point toward or away from treatment. For these patients, the score can tip the decision.
Guidelines from the American College of Cardiology and American Heart Association are straightforward at the extremes. A score of zero in an otherwise borderline-risk adult is reason to hold off on statin therapy and focus on lifestyle changes. A score above 100 generally triggers a recommendation to start a statin, regardless of what traditional risk calculators show. For scores between 1 and 99, the decision is more individualized. Canadian guidelines describe this range as still intermediate, where shared decision-making between you and your doctor makes the most sense.
For adults between 76 and 80 with borderline cholesterol levels, the ACC/AHA guidelines specifically note that a zero score supports deferring statin therapy. This is one of the few situations where a single test result can directly change a prescribing decision in older adults.
Cost and Insurance Coverage
Because the calcium score scan hasn’t become part of universal screening guidelines, insurance coverage is inconsistent. Some plans cover it, particularly if your doctor documents that you’re in an intermediate risk category. Many people pay out of pocket. Prices vary by location but typically fall between $75 and $300 at imaging centers, making it one of the more affordable cardiac tests available.
What the Score Cannot Tell You
The Agatston score measures calcified plaque only. It tells you nothing about non-calcified, or “soft,” plaque, which can be just as dangerous. In fact, soft plaque is the type most likely to rupture and cause a sudden heart attack. A published case review in JACC noted that the absence of coronary calcification does not rule out atherosclerotic plaque, because non-calcified deposits simply don’t register on the scan.
The score also doesn’t show whether a specific artery is narrowed enough to restrict blood flow. Two people with the same Agatston score can have very different anatomy: one might have calcium spread thinly across several arteries with no real blockage, while another might have a concentrated deposit narrowing a single vessel. If your doctor suspects an active blockage, they’ll order additional imaging, such as a CT angiogram or a stress test, rather than relying on the calcium score alone.
Finally, the score is a snapshot in time. Calcium deposits don’t shrink with medication or lifestyle changes. Statins slow the rate of new plaque formation and stabilize existing plaque, but they can actually cause a modest increase in your calcium score over time. A rising number on a repeat scan doesn’t necessarily mean your risk is getting worse if you’re on treatment. For this reason, most guidelines discourage routine repeat scanning just to track your score.