CT Coronary Calcium Score Explained: A Complete Guide to Your Results

A CT coronary calcium score is a non-contrast CT scan that measures calcified plaque in the coronary arteries — the vessels supplying blood to the heart — and reports the result as a single number called an Agatston score, ranging from 0 (no plaque) to the thousands (extensive plaque).

The higher the number, the more calcified plaque is present, and the greater the associated risk of coronary artery disease. Because calcium buildup is one of the earliest visible signs of atherosclerosis, the test is often used to help adults without symptoms assess their long-term risk of heart attack before it becomes a problem.

This guide covers how the test works, how to read your score, what it costs, and what to do next.

A CT coronary calcium score, also called a coronary artery calcium (CAC) score, cardiac calcium score, or coronary calcium scan, is a specialized CT scan of the heart that detects and quantifies calcium deposits in the coronary arteries, according to the American Heart Association. It uses no injected contrast dye and takes only a few minutes to perform.

Calcium in the coronary arteries is a marker of atherosclerosis: the buildup of plaque, a waxy mixture of cholesterol, fat, and other substances, on the artery walls. As plaque ages, part of it hardens and calcifies. The calcium itself isn't what causes disease, but it's a reliable proxy for how much total plaque, including soft, non-calcified plaque the scan can't directly see, has accumulated in the arteries over time.

These terms are used interchangeably in most clinical and patient materials. "Coronary calcium score," "coronary artery calcium (CAC) score," "cardiac calcium score," "coronary calcium scan," and "heart scan" all typically refer to the same non-contrast CT test. "Score" refers to the numeric result; "scan" or "CT" refers to the imaging procedure that produces it.

The number generated by a coronary calcium scan is called the Agatston score, named for the cardiologist who developed the scoring method in 1990. CT software identifies calcified areas in each coronary artery, measures their density and area, and combines those measurements into a weighted score for that artery.

The scores from all the coronary arteries are added together to produce the total Agatston score reported to your doctor.

Because it factors in both the density and the area of calcium deposits, the Agatston score weights larger and denser deposits more heavily. It remains the most widely used and clinically validated calcium-scoring method, though some centres also report a related measure, the calcium volume score.

A coronary calcium scan is quick, non-invasive, and doesn't require an IV line or contrast dye. Here's what the full coronary calcium score procedure involves, from preparation to your results.

Preparation is minimal:

• Avoid food, caffeine, and tobacco for about four hours beforehand — caffeine and nicotine raise heart rate, which can affect image quality and scoring accuracy.

• Continue taking your regular medications, including heart medications, unless your provider tells you otherwise.

• Wear clothing without metal (zippers, snaps, underwire) and leave jewellery, eyeglasses, and hairpins at home, since metal can interfere with the images.

During a cardiac CT calcium score exam, you'll lie on your back on a table that slides into a large, open, doughnut-shaped CT scanner. A technologist places sticky electrode patches on your chest to record your EKG; the scanner times each image to your heartbeat to keep the pictures sharp.

The table moves slowly through the scanner, and you'll be asked to hold your breath for several seconds at a time while images are captured to evaluate calcium in the heart's arteries, not blood flow.

The full appointment, including setup, usually takes about 10 to 15 minutes, and the scan itself takes only a few minutes.

A coronary calcium scan uses a low, targeted radiation dose about the same amount as the natural background radiation a person absorbs over about one year. Because there's no injected contrast, there's no risk of a contrast reaction. As with any test that uses radiation, it's generally reserved for adults with an appropriate clinical reason for testing rather than for repeated routine use.

Your total Agatston score range falls into one of several general risk categories, and higher scores generally mean more calcium detected and greater heart disease risk:

The raw Agatston number only tells part of the story. What often matters more clinically is how your score compares to others of the same age, sex, and ethnicity expressed as a percentile. A score of 150 in a 45-year-old is far more concerning than the same score in a 75-year-old, because calcium naturally accumulates with age.

Clinicians often use tools such as the MESA (Multi-Ethnic Study of Atherosclerosis) calculator to convert a raw Agatston score into an age-, sex-, and ethnicity-adjusted percentile, which gives a clearer picture of relative risk than the raw number alone.

On the coronary calcium score chart, a score of 100 sits in the mild-to-moderate range and reflects how much calcium is present in the coronary arteries; how concerning it is depends heavily on age, and scores in this range help estimate the risk of heart disease or a future heart attack. 100 is a high finding at 45 but closer to average at 75.

A score above 400 indicates an extensive calcium burden and is considered strong evidence of significant coronary artery disease, and it generally prompts further cardiology evaluation. See the FAQ section below for more on specific score thresholds.

Coronary calcium scoring is generally intended for adults who don't have symptoms of heart disease but are at moderate risk when traditional risk factors do not fully clarify their risk. The general calcium score test age recommendation from the American Heart Association and the American College of Cardiology is roughly 40 to 75 years old.

Risk is typically estimated using traditional factors — family history, cholesterol levels, blood pressure, smoking history, or a formal tool such as the ASCVD risk estimator.

In this group, the score can refine risk assessment. It can improve early detection of coronary artery disease before symptoms appear, help estimate future coronary artery disease risk, and clarify whether more aggressive prevention, such as starting a statin, is warranted, or whether estimated risk is low enough to hold off.

The test is typically not recommended for people already diagnosed with coronary artery disease (CAD), people at very low estimated risk, or people at very high risk who would be treated aggressively regardless of the result; the score is unlikely to change management in these cases.

It's also generally not used under age 40, since calcification is uncommon at that age even in people who go on to develop disease later.

Guideline bodies don't fully agree on this point: the American College of Cardiology, American Heart Association, and Society of Cardiovascular Computed Tomography all support considering CAC testing in select adults, while the U.S. Preventive Services Task Force (USPSTF) has concluded there is currently insufficient evidence to recommend it as a routine addition to standard risk assessment.

Your healthcare team can help decide whether calcium scoring fits your personal risk profile. MyDiagnostics' Comprehensive Heart Health Check-Up can also help establish your baseline cardiac risk factors before deciding on a calcium score test.

A coronary calcium scan is billed under CPT code 75571 — sometimes searched as the calcium score test CPT code. Because most insurers, including Medicare, classify it as a screening test rather than a diagnostic one, coverage is inconsistent:

• Medicare generally does not cover calcium scoring; providers are required to have patients sign an Advance Beneficiary Notice (ABN) before billing for it.

• Most commercial insurers also don't routinely cover the test, though some plans cover it selectively when specific risk factors are documented.

• Many hospitals and imaging centres offer it as a self-pay test at a fixed, relatively low out-of-pocket price, precisely because so few patients have coverage.

Given the variability in coverage, it's worth calling both your insurer and the imaging centre directly to confirm expected cost before scheduling. MyDiagnostics offers a Comprehensive Heart Health Check-Up (ECG, TMT & 2D Echo) as a starting point for cardiac risk assessment; get in touch to discuss whether a coronary calcium score is the right next step for you.

This is one of the most common questions after a high result, and the honest answer is nuanced. Once plaque has calcified, it generally doesn't disappear; an Agatston score essentially never decreases on its own, and no diet or lifestyle change has been shown to reliably lower the number itself.

Statins are often prescribed after a high calcium score, but their effect on the score itself is counterintuitive. Randomized trial data published in the Journal of the American College of Cardiology and similar studies have generally failed to show that statins reduce Agatston scores, and in some cases scores rise on statin therapy because statins tend to stabilize soft, vulnerable plaque by converting it into denser, more calcified, and safer plaque. 

In other words, a rising score while on a statin isn't necessarily bad news; it can reflect plaque stabilization rather than disease progression. What reliably reduces cardiovascular risk, independent of the calcium number, is standard risk-factor management: controlling LDL cholesterol and blood pressure, following a heart-healthy diet, not smoking, staying physically active, managing diabetes, and maintaining a healthy weight. Rather than trying to lower the score itself, most cardiologists recommend treating the underlying risk factors the score revealed.

A high or unexpectedly elevated score is worth discussing with your doctor or a cardiologist because it signals increased risk rather than serving as a diagnosis by itself. Typical next steps include a detailed risk-factor review (cholesterol, blood pressure, blood sugar), a conversation about starting or intensifying statin therapy, and lifestyle counselling.

In some cases, your doctor may recommend additional testing in other tests such as a stress test or CT coronary angiography, depending on symptoms or suspected blockages, to check whether any blockages are significantly limiting blood flow. The calcium score is a starting point for a prevention conversation, not a standalone diagnosis.

Ready to build a fuller picture of your cardiac risk? MyDiagnostics' Comprehensive Heart Health Check-Up (ECG, TMT & 2D Echo) is a convenient next step for baseline risk-factor screening before or alongside a coronary calcium score.

A coronary calcium score is one of several diagnostic tests used to assess heart health in different ways, and coronary artery calcium scoring can complement standard risk measures when risk remains uncertain:

A coronary calcium score is one part of a complete cardiac risk picture. MyDiagnostics is India's leading digital health clinic, and our Comprehensive Heart Health Check-Up (ECG, TMT & 2D Echo) with home-based ECG and easy scheduling for TMT and 2D Echo is a convenient way to build your baseline cardiac risk profile.

You can also explore our Total Health Comprehensive full-body checkup for broader preventive screening. Contact MyDiagnostics to discuss whether a coronary calcium score, or another cardiac screening, is the right next step for you.