What Is a Coronary Artery Calcium Score?
A coronary artery calcium (CAC) score — sometimes called a "calcium score" or "heart scan" — is a specialized CT scan that measures the amount of calcified plaque in the walls of the arteries that supply your heart. It takes about 10–15 minutes, requires no dye or needles, and gives your doctor a concrete number that reflects how much plaque has already built up in your coronary arteries.
Calcium deposits in artery walls are a hallmark of atherosclerosis — the process where plaque accumulates over time and narrows blood vessels. Where there's calcium, there's plaque. The more calcium, the more plaque, and the higher the risk of a heart attack down the road.
Think of it as a "plaque report card" for your heart. Standard risk calculators estimate your future risk based on factors like age, cholesterol, and blood pressure. The CAC score tells you what's actually happening inside your arteries right now — making it one of the most powerful tools in preventive cardiology.
Understanding Your Score
The result is reported as a number — the Agatston score — calculated based on the density and volume of calcium deposits found. Here's what the numbers mean for your risk and treatment:
0 — No hardened plaque detected. No atherosclerosis visible on scan. Very low risk of heart attack in the next 10 years. Reassuring, but not a permanent pass — lifestyle still matters.
1–100 — Atherosclerosis present. You have calcified plaque in your arteries. Moderate risk. Aspirin is generally not recommended at this level unless you have other high-risk features. Focus on statins (if indicated) and aggressive lifestyle modification. Close monitoring recommended.
>100 — Atherosclerosis present. Significant plaque burden. Higher risk. Aspirin is likely beneficial for primary prevention at this level. High-intensity statin recommended. Blood pressure and diabetes management become critical. Frequent monitoring and possible cardiology follow-up.
Key point: Any score above 0 means you have atherosclerosis — hardened plaque is present in your arteries. The higher the score, the more plaque burden you carry, and the more aggressive your prevention strategy should be.
Who Should Get a CAC Score?
The CAC score is most useful for people in the "intermediate risk" zone — those who fall in a gray area where a doctor isn't sure whether to start preventive medications like a statin. The score helps tip the decision in one direction or the other.
The ACC/AHA guidelines recommend considering a CAC score for:
- Adults aged 40–75 with a 10-year cardiovascular risk between 7.5–20% (intermediate risk)
- People who are uncertain about starting statin therapy and want more information before deciding
- Adults with a family history of early heart disease who want to know their personal risk
- People with risk factors (diabetes, hypertension, high cholesterol) who have never had a cardiac event and want a clearer risk picture
If you've already had a heart attack, bypass surgery, or stents — you already have established heart disease and don't need a CAC score. It's a screening tool for people who haven't yet had a cardiac event.
A CAC score of zero is also valuable — it's one of the most reassuring findings in preventive cardiology. Studies show that people with a zero score have an extremely low risk of heart attack over the next 10–15 years, even if other risk factors are present. This can support a decision to hold off on medications while focusing on lifestyle changes.
What to Expect During the Test
The CAC scan is quick, painless, and requires no special preparation in most cases:
- You'll lie on a CT scanner table. The scan itself takes only a few minutes.
- No contrast dye is injected — unlike a coronary CT angiogram.
- You'll be asked to hold your breath briefly during the scan.
- The radiation dose is low — roughly equivalent to a mammogram.
- Results are typically available within a few days and reviewed with your doctor.
The test is usually done at a hospital radiology department or outpatient imaging center. It's often not covered by insurance when used for screening (i.e., no symptoms), but it typically costs $75–$200 out of pocket — a worthwhile investment for the information it provides.
What Your Score Does (and Doesn't) Tell You
What a CAC score TELLS you:
The simple bottom line: Your CAC score tells you whether you have atherosclerosis in your coronary arteries, and how much plaque burden you likely have. Any score above 0 means you have plaque in your arteries.
- Score of 0: No calcified plaque detected. Very low risk of heart attack in the near term.
- Score of 1–99: You have plaque present. Mild to moderate plaque burden.
- Score of 100–299: Meaningful plaque burden. Moderate to high risk.
- Score of 300+: Extensive plaque. High risk. Close cardiology follow-up needed.
What a CAC score DOES NOT tell you:
- It doesn't tell you about blockages. The CAC score measures calcium, not how narrowed your arteries are. You could have a high score with no significant blockages, or have an artery that's critically narrowed with a lower score. If your doctor is concerned about blockages, you'd need a coronary CT angiogram (CCTA) or stress test — not a calcium score.
- It doesn't show you WHERE the plaque is. A CAC score gives you a total plaque burden number, but it doesn't pinpoint which arteries are affected or how severe individual lesions are. That level of detail requires CCTA or cardiac catheterization.
- It doesn't guarantee you're safe. A score of 0 is reassuring but doesn't mean your arteries are completely clear. Soft, non-calcified plaque can be present with a zero score — it just hasn't calcified yet. Lifestyle still matters.
- It doesn't detect non-calcified plaque. Young people, in particular, can have significant soft plaque with zero calcium. This is why a zero score in a 45-year-old with a strong family history of early heart disease should still prompt lifestyle optimization.
CAC Score = "Do I have plaque?" | CCTA = "How much is blocking my artery?"
These are two completely different tests. Don't confuse them. If your doctor is worried about a blockage causing your symptoms, you need CCTA or a stress test. A CAC score alone won't answer that question.
What happens next — treatment decisions:
Your CAC score helps your doctor decide on preventive treatment. Here's the typical approach:
- Score of 0: Reassurance. Focus on maintaining healthy habits. May repeat in 5 years if risk factors persist. Statin may be reasonably deferred in many cases.
- Score of 1–99: Lifestyle counseling. Moderate-intensity statin often recommended. Close follow-up to prevent progression.
- Score of 100+: High-intensity statin is generally recommended. Blood pressure and diabetes targets become more strict. Aspirin may be considered in selected patients. More frequent monitoring.
- Score of 300+: Aggressive risk reduction. Possible additional testing (like CCTA if symptoms develop). Cardiology referral if not already established.
Important: A CAC score is one piece of the puzzle — not the whole picture. Your doctor will interpret it in the context of your overall health, family history, lifestyle, other test results, and most importantly, whether you have any symptoms. Never make medication decisions based on your score alone.
Limitations of the CAC Score
The CAC score is a powerful tool, but it's not perfect. Understanding what it can't tell you is just as important as understanding what it can.
It only detects calcified plaque
The scan measures calcium deposits — a sign of older, more stable plaque. It does not detect soft, non-calcified plaque, which is actually more prone to rupture and cause heart attacks. A score of zero doesn't mean your arteries are completely clear — it means there's no calcified plaque yet. Young people in particular may have significant soft plaque with a zero CAC score.
It doesn't show blockages
A high CAC score tells you there's plaque present, but it can't tell you how much any single artery is narrowed. For that, you'd need a coronary CT angiogram (CCTA) or a stress test. CAC is a risk stratification tool — not a diagnostic one.
Limited usefulness at the extremes of age
In adults under 40, the test is rarely useful — plaque simply hasn't had time to calcify, so scores are almost always zero even if risk factors are accumulating. In adults over 75, nearly everyone has some calcium, making the score less discriminating. The sweet spot is roughly ages 40–70, where the test adds the most information beyond standard risk calculators.
Radiation exposure (small but real)
The scan involves a low dose of radiation — roughly equivalent to a mammogram or a few chest X-rays. For most adults in the appropriate age range, the benefit of the information far outweighs this risk. However, it's a reason not to repeat the test unnecessarily.
Not covered by insurance for screening
Most insurance plans don't cover the CAC scan when used as a screening test in asymptomatic patients. Out-of-pocket cost is typically $75–$200 — a relatively small investment for the clinical information it provides, but worth knowing in advance.
It can cause anxiety
Finding unexpected calcium — especially in someone who felt perfectly healthy — can cause significant anxiety and may lead to downstream testing that isn't always necessary. This is why the test is most valuable when ordered thoughtfully, with a clear plan for how to act on the results.
Bottom line: The CAC score is one of the best tools we have in preventive cardiology — but it works best as part of a broader conversation with your doctor, not as a standalone test you order on your own.
📺 Video Resources
Watch Dr. Pollock explain the coronary artery calcium score and what it means for your heart health.
When to Ask Your Doctor About a CAC Score
Bring it up at your next appointment if:
- You're between 40–75 and have never discussed your 10-year heart attack risk with a doctor
- Your doctor has suggested a statin and you're on the fence about starting one
- A parent or sibling had a heart attack before age 55 (men) or 65 (women)
- You have multiple risk factors but feel fine and want a clearer picture of where you stand
- You want a more personalized, data-driven approach to your heart health
If you're having chest pain, shortness of breath, or any symptoms that concern you right now, call 911 or go to an emergency room. Don't schedule a scan.