A normal calcium score is zero. This means no calcified plaque was detected in your coronary arteries, and it’s the best possible result on a coronary artery calcium (CAC) scan. Any score above zero indicates at least some calcium buildup in the arteries that supply blood to your heart. But what counts as “normal” also depends on your age, sex, and ethnicity, since calcium naturally accumulates as you get older.
How the Scoring Ranges Work
The CAC scan uses a CT scanner to take images of your heart and measure calcified deposits in your coronary arteries. The result is reported as an Agatston score, named after the physician who developed the method. The ranges break down like this:
- 0: No calcium detected. This is considered ideal.
- 1 to 99: Mild plaque deposits. Some calcium is present but the buildup is relatively small.
- 100 to 300: Moderate plaque deposits, indicating more significant arterial calcification.
- Over 300: Extensive plaque deposits and a higher risk of heart attack.
These ranges give you a rough sense of where you stand, but they don’t tell the whole story. A score of 50 means something very different for a 45-year-old woman than for a 75-year-old man.
Why Age, Sex, and Ethnicity Matter
Coronary calcium increases with age, and men tend to accumulate it earlier and faster than women. Only about one-third of middle-aged women have any detectable calcium at all. A score of 25 in a 48-year-old man might place him at a relatively high percentile for his age group, while the same score in a 72-year-old could be quite typical.
The Multi-Ethnic Study of Atherosclerosis (MESA), a large research project tracking cardiovascular health across racial and ethnic groups, developed a widely used tool that compares your score against people of the same age, sex, and ethnicity. Rather than just looking at your raw number, your doctor can see whether your score falls at the 25th percentile or the 90th percentile for your demographic. A score at or above the 75th percentile is considered elevated regardless of the raw number. The MESA tool covers adults aged 45 to 84 who identify as White, African American, Hispanic, or Chinese.
What a Score of Zero Really Means
A zero score is reassuring, but it’s not a guarantee against heart disease. Roughly one-quarter to one-third of all cardiovascular events happen in people whose calcium score is zero. That’s because the scan only detects calcified plaque. Softer, non-calcified plaque, which can also rupture and cause a heart attack, doesn’t show up on this test.
Still, a zero score is clinically meaningful. The 2019 prevention guidelines from the American College of Cardiology and American Heart Association note that people with a calcium score of zero generally have low enough 10-year event rates that statin therapy may offer limited benefit. For many people in an intermediate risk category, a zero score can be the deciding factor against starting cholesterol medication.
How Scores Affect Treatment Decisions
CAC scoring is most useful for people whose heart disease risk falls in a gray zone. If your estimated 10-year risk of a cardiovascular event is between 5% and 20% based on standard factors like cholesterol, blood pressure, and family history, the calcium score can tip the decision on whether to start a statin.
The guidelines are specific: for adults in this intermediate risk range, a calcium score of 100 or higher (or a score at or above the 75th percentile for your age and sex) makes starting statin therapy reasonable. People with scores of 1 to 99 fall into a less clear-cut category. Their 10-year event rates vary by age: about 3.8% for adults 45 to 54, 6.5% for those 55 to 64, and 8.3% for adults 65 to 74. At these levels, the risk reclassification is modest, so the typical recommendation is to revisit the conversation with your doctor rather than automatically begin medication.
Patients with a CAC score of 1 to 100 have roughly double the risk of a cardiovascular event compared to those with a score of zero. Once scores climb above 300, the risk increases substantially, and aggressive preventive treatment becomes a higher priority.
What the Scan Can and Cannot Detect
A CAC scan is excellent at finding hard, calcified plaque. It’s fast, noninvasive, and exposes you to a low dose of radiation: about 1 to 2 millisieverts, which is roughly equivalent to one to two years of natural background radiation from the environment.
The key limitation is that it cannot detect soft plaque. These non-calcified deposits can be just as dangerous, sometimes more so, because they’re more prone to rupturing and triggering a clot. This is one reason why a zero calcium score doesn’t eliminate risk entirely. The scan also focuses on coronary arteries and may underestimate stroke risk, since it doesn’t evaluate the carotid arteries that supply blood to the brain.
For people with very high calcium scores (400 and above), some cardiologists recommend additional testing that looks at how well blood actually flows through the heart muscle. Research published in an American Heart Association journal found that among patients with scores of 1,000 or higher, those with preserved blood flow through the heart had a 56% lower rate of cardiac events compared to those whose flow was impaired. In other words, a high calcium score is concerning, but functional testing can help distinguish between stable calcification and disease that’s actively restricting blood flow.
When to Repeat the Scan
If your initial score is zero, there’s generally no urgency to repeat the scan in the near term. Calcium doesn’t appear overnight, and serial scanning for low-risk individuals adds radiation exposure without changing management. Many clinicians suggest waiting five years or longer before rescanning if risk factors haven’t changed significantly.
If your score is above zero, the decision about repeat testing depends on what treatment you’ve started and whether your risk profile has shifted. The scan isn’t typically used to track whether medications are “working,” since statins can actually slow plaque progression without necessarily lowering the calcium score. Your doctor will focus on cholesterol levels, blood pressure, and other modifiable risk factors to gauge progress rather than ordering frequent repeat scans.