2025 Update on this Key Heart Risk Test

Estimated reading time: 12 minutes

Coronary calcium score is a simple, non-invasive scan that reveals hidden plaque and helps predict your risk of heart disease.

Your cholesterol may look perfect. You may feel healthy. But silently, beneath the surface, plaque can build inside your coronary arteries — and you’d never know it.

That’s where the coronary calcium score (CAC score) comes in.

A coronary calcium scan is a quick, non-invasive CT test that detects tiny calcium deposits in the walls of the coronary arteries — a telltale sign of atherosclerosis, the disease that causes most heart attacks.

Calcium itself isn’t dangerous. In fact, it’s part of the body’s healing response. However, when it appears in the coronary arteries, it reveals something important: atherosclerosis has already begun.

By measuring the total burden of calcium, the CAC score helps uncover hidden cardiovascular risk, often before symptoms appear, and long before traditional risk calculators raise red flags.

In this article, I’ll explore:

• What the coronary calcium score measures — and what it doesn’t
• How CAC scores are interpreted — and what they mean for your heart
• Who benefits most from CAC testing
• How CAC helps guide treatment decisions, including statin use
• How it compares to other CT-based heart scans

This article was originally published in 2014, updated in 2020, and fully revised again in 2025 to reflect the latest research and clinical guidelines. I’ve also kept all the original comments to preserve the thoughtful questions and insights shared by readers over the years. Thank you for making this one of the most visited and discussed articles on DocsOpinion.

What Is Coronary Calcium Score?

A coronary calcium score is a number. But behind that number is a picture — a snapshot of your coronary arteries that reveals whether silent atherosclerosis is already present.

The test is called a coronary artery calcium (CAC) scan, and it uses a special type of CT (computed tomography) imaging to look for one thing: calcium deposits in the walls of your coronary arteries. These deposits are not floating in the bloodstream. They’re embedded in the artery walls, often as part of older, more stable plaque.

The more calcium present, the more plaque you’ve accumulated over time.

The technique was pioneered in the late 1980s by cardiologist Dr. Arthur Agatston, who developed a method for quantifying coronary calcification using ultrafast CT imaging, which is now known as the Agatston score.

Once the scan is complete — it usually takes less than 10 minutes — a computer assigns a score based on the extent and density of the calcification. The result is your coronary calcium score.

Importantly, this is not a stress test. There are no treadmills, no injections, no contrast dye, and no IVs. You simply lie flat in a CT scanner, hold your breath for a few seconds, and let the machine do the rest.

A score of zero means no detectable calcified plaque — and that’s very reassuring. A higher score indicates more plaque and an increased long-term risk of heart attack, even in the absence of symptoms.

What the CAC Score Tells Us – and Doesn’t

The coronary calcium score is a powerful tool for assessing cardiovascular risk. But like all tests, it has limits.

What It Tells Us

The CAC score tells us whether there’s calcified plaque in the coronary arteries — and how much. That’s significant because calcium doesn’t appear in healthy arteries. It’s a marker of chronic inflammation and arterial injury.

Studies show that CAC scoring outperforms LDL cholesterol and many traditional risk markers in predicting future cardiac events, especially in asymptomatic individuals who appear low risk on paper.

What It Doesn’t Tell Us

• It doesn’t detect soft (non-calcified) plaque, which may still pose a risk.

• It doesn’t show blockages or blood flow limitation.

• It reflects cumulative damage, not recent changes.

So how should we use it?

As a risk detector — not a diagnostic test.
As a decision aid — not a crystal ball.
And as a motivator — to support prevention before disease manifests.

Who Benefits From a CAC Scan

The CAC scan is most effective when traditional tools leave us uncertain — when someone is neither clearly low-risk nor clearly high-risk, and treatment decisions are up for discussion.

The Sweet Spot: Intermediate Risk

Guidelines recommend CAC scoring for adults aged 40–75 who have an intermediate 10-year ASCVD risk, typically between 5% and 20%.

ASCVD stands for Atherosclerotic Cardiovascular Disease, which includes heart attack, stroke, and other forms of arterial disease. The 10-year ASCVD risk is typically calculated using online tools, such as the Pooled Cohort Equations, which take into account age, cholesterol levels, blood pressure, smoking status, and other relevant factors.

Here’s how CAC results guide decisions in this group:

• CAC = 0 → Very low short-term risk; may safely defer statin therapy

• CAC 1–99 → Consider statin if age ≥55 or additional risk factors present; decision should be individualized

• CAC >100 or ≥75th percentile → Elevated risk; statin generally recommended

What does “≥75th percentile” mean? It means your calcium score is higher than 75% of people your age and sex, which signals an unusually high plaque burden compared to your peers.

Other Good Candidates

• Strong family history of premature coronary disease

• Elevated Lp(a) or abnormal triglyceride/HDL levels despite normal LDL

• Individuals unsure about starting a statin and looking for more personalized information

When It is Not Helpful

• Already high-risk: People with known ASCVD, diabetes plus other risk factors, or LDL cholesterol ≥190 mg/dL

• Clearly low-risk: Young, healthy individuals without risk factors

• Acute symptoms: Chest pain or suspected heart attack should be evaluated with CTA, ECG, or other emergent tools, not CAC scanning

CAC and Treatment Decisions

Now that we’ve identified who benefits most from CAC scanning, the next step is understanding how the results guide treatment. Whether the score is zero or in the hundreds, each level provides a distinct signal that helps personalize prevention.

The CAC score isn’t just a number — it’s a guidepost. It helps clinicians and patients tailor prevention strategies based on the actual presence of atherosclerosis, not just risk factors on paper.

🟢 CAC = 0

A CAC score of zero is a strong negative risk marker. Most individuals with a zero score have a very low chance of a heart attack in the next 5–10 years, even if cholesterol is borderline or family history is concerning.

In this setting, it’s often reasonable to focus on lifestyle and defer statin therapy, especially in younger or statin-hesitant patients.

🟡 CAC 1–99 and 100–399

A CAC score between 1 and 99 suggests that atherosclerosis has begun. In adults over 55, even a low score may tip the balance in favor of statin use.

A score from 100 to 399 is more definitive. At this level, guidelines generally favor statin therapy because the overall plaque burden is high.

🔴 CAC ≥400

A CAC ≥ 400 places a patient in a high-risk category. Even without symptoms, this level of plaque burden is associated with a markedly increased likelihood of future cardiovascular events. Treatment at this stage usually includes statin therapy, lifestyle optimization, and sometimes aspirin or further imaging.

Using CAC Score to Assess Arterial Age

It is important to note that interpretation varies by age and sex. For example, women generally have lower calcium scores than men. That’s why percentile-based comparisons — such as whether your score falls above the 75th percentile — matter.

A helpful way to visualize this is through the concept of arterial age — an estimate of how old your arteries appear based on your CAC score.

The calcium score tends to increase with age. At a certain age, a given CAC score may be considered ‘normal’ or ‘accelerated,’ depending on how it compares to population averages.

If your arterial age matches your chronological age, that’s expected. But if your arterial age is much older, that suggests accelerated vascular aging — and higher risk.

For example:

A 60-year-old man with a CAC score of 500 has an estimated arterial age of 84. His arteries resemble those of an average 84-year-old man.

This framing can help personalize prevention. It’s one thing to know your risk is elevated; it’s another to be told, “Your arteries look 24 years older than you.”

📈 You can estimate arterial age and score distribution based on age, sex, and ethnicity using tools like the MESA Risk Score and Coronary Age Calculator and the MESA Arterial Age Calculator.

Here you can see reference values for CCS according to age and gender.

Calcium Score vs Coronary CT- What’s the Difference?

While the CAC score is a valuable tool for detecting silent coronary artery disease and guiding preventive strategies, it’s not the only CT-based scan available. One of the most important comparisons is with coronary CT angiography (CTCA), which is used to evaluate symptoms and visualize both soft and calcified plaque.

In short:

• CAC is best suited for asymptomatic individuals to uncover hidden risk and guide prevention.

• CTCA is designed to evaluate symptoms, detect soft plaque, and assess vessel narrowing.

Both tests have their place. The key is knowing which question you’re trying to answer: Are we looking for hidden risk — or active disease?

For a full comparison, see: 👉 CT Coronary Angiography vs. Calcium Score: What’s the Difference?

In short:

• CAC is best suited for asymptomatic individuals to uncover hidden risk and guide prevention.

• CTCA is designed to evaluate symptoms, detect soft plaque, and assess vessel narrowing.

Both tests have their place. The key is knowing which question you’re trying to answer: Are we looking for hidden risk — or active disease?

Limitations and Considerations

The coronary calcium score is powerful — but like every medical test, it has limitations. Understanding what the CAC scan doesn’t show is key to using it wisely and avoiding false reassurance.

It Doesn’t Detect Soft Plaque

A CAC scan only sees calcified plaque. It completely misses soft (non-calcified) plaque — the type that’s often more vulnerable and more likely to rupture. Especially in younger individuals or those with high inflammation or elevated Lp(a), soft plaque can still pose risk even when the calcium score is zero.

It Doesn’t Show Blockages

A high CAC score reflects the total burden of plaque, but it doesn’t indicate whether blood flow is restricted. A person with a score of 300 could have wide, stable plaque and no obstruction. Another person with a score of 30 might have a focal, flow-limiting lesion. If symptoms are present, functional or anatomical testing (like CTA or stress imaging) is needed.

It’s Less Useful in Certain Groups

• People with known coronary artery disease (CAD): They’re already high risk — a CAC score won’t change management.

• People on statins: Statins can increase plaque calcification while reducing inflammation, making the score less informative.

• Very young adults: A zero score doesn’t exclude early non-calcified disease.

• Emergency settings: CAC is not appropriate for evaluating acute chest pain.

It Involves Radiation (Though Minimal)

A CAC scan delivers a small amount of radiation — usually under 1 millisievert. That’s about the same as a mammogram, and far less than a CT angiogram. It’s safe for most people but worth noting if multiple scans are planned over time.

Final Thoughts: A Simple Test, A Powerful Message

The coronary calcium score doesn’t predict the future — but it helps you shape it.

Whether your score is zero or in the hundreds, the CAC scan translates decades of silent exposure into visible, actionable insight. It takes risk from the abstract to the concrete.

For some, it brings relief: a clean slate, and the chance to stay that way through smart choices.

For others, it brings clarity: disease is present — maybe silently — and now is the time to act.

Either way, the message is the same: you have agency. You can slow the process. You can target the right therapy. You can make prevention personal.

And that’s the real power of the calcium score — not just revealing risk, but helping you do something about it.