A coronary calcium scan (CAC scan) is a specialized CT imaging test that detects calcium deposits in the walls of your coronary arteries—a marker of atherosclerosis. The resulting CAC score quantifies the amount of calcium and predicts your cardiovascular risk more accurately than traditional risk factors alone.
If your cardiologist has recommended a CAC scan or you've already received a score, understanding what the number means—and what it doesn't—is essential for making informed health decisions.
What the CAC Score Measures
Calcium doesn't cause atherosclerosis; rather, calcium deposits form as part of the atherosclerotic process. When LDL cholesterol particles penetrate the arterial wall, they trigger inflammation. The body responds by depositing calcium in the plaque, stabilizing it but also creating a visible marker on imaging.
The Agatston score standardizes calcium quantification:
- Scores are calculated by multiplying the area of calcium deposits by their density
- Higher scores indicate greater plaque burden
- CAC is present in ~25-35% of asymptomatic middle-aged adults
Key insight: Calcium in arteries ≠ calcium in bones. High coronary calcium doesn't mean your bones are calcium-rich; these are independent phenomena. You can have strong bones and significant coronary calcium, or vice versa.
CAC Score Ranges and What They Mean
| CAC Score | Category | Interpretation | 10-Year Risk* |
|---|---|---|---|
| 0 | Absent | No detectable coronary calcium | 1-3% |
| 1-99 | Minimal | Mild atherosclerosis present | 4-7% |
| 100-299 | Mild to Moderate | Moderate plaque burden | 8-15% |
| 300-399 | Moderate to Severe | Significant disease | 15-20% |
| 400+ | Severe | Extensive atherosclerosis | 20%+ |
*10-year risk of myocardial infarction or coronary death in asymptomatic individuals; varies by age and additional factors.
CAC = 0: The Favorable Scenario
A score of zero indicates no detectable coronary calcium—a strong reassurance. Studies show that 90-95% of people with CAC=0 remain free of cardiovascular events over 10 years.
This doesn't mean zero risk, however. Approximately 5-10% of CAC=0 individuals still experience events, particularly if they:
- Have metabolic syndrome (obesity, insulin resistance, high triglycerides)
- Possess extremely high LDL or ApoB despite no calcium
- Have high-risk genetic markers (familial hypercholesterolemia)
- Smoke or have severe diabetes
- Exhibit significant coronary artery disease risk on other measures
If you have CAC=0:
- Continue monitoring cholesterol and metabolic markers annually
- Maintain healthy lifestyle (exercise, Mediterranean diet, sleep, stress management)
- Repeat scanning every 5-10 years if you remain low-risk
- Escalate screening frequency if risk factors emerge
CAC = 1-99: Mild Atherosclerosis
This range indicates detectable but minimal calcium—early atherosclerosis. Risk varies significantly based on age-adjusted percentiles:
- 75th percentile: You're at the upper limit for your age—consider more aggressive risk factor management
- 50th percentile: Average for your age
- 25th percentile: Better than average for your age
A score of 50 in a 40-year-old (very high for age) warrants more aggressive treatment than a score of 80 in a 65-year-old (lower for age). Your cardiologist uses percentile charts, not just absolute scores, to assess your relative risk.
Management: Most guidelines recommend statin therapy for scores in this range, particularly if LDL, ApoB, or other risk factors are elevated. Aggressive risk factor modification and 2-3 year follow-up scanning assess progression.
CAC = 100-399: Moderate Disease
Scores above 100 indicate significant atherosclerosis. Medical treatment—usually with statins—is typically recommended regardless of cholesterol levels, as the presence of calcium indicates existing disease.
These individuals have 10-year event risk of 8-20%, though risk varies with LDL, metabolic health, and other factors.
Management: Statin therapy is standard. Many cardiologists also consider aspirin therapy (after age 40 or with multiple risk factors). Aggressive LDL control targeting ApoB <80 mg/dL is often recommended. Follow-up scans every 2-3 years assess disease progression.
CAC ≥ 400: Extensive Disease
Scores of 400+ indicate significant atherosclerosis with substantial event risk (20%+). These individuals have clinical coronary artery disease even if they haven't had a heart attack.
Management: Aggressive medical therapy is standard, typically including:
- High-intensity statins (targeting LDL <70 mg/dL or ApoB <55 mg/dL)
- Consideration of additional agents (ezetimibe, PCSK9 inhibitors, bempedoic acid)
- Aspirin therapy
- Beta-blockers and ACE inhibitors if additional risk factors present
- Possible cardiac catheterization and revascularization depending on symptoms
Age Adjustment and Percentile Context
CAC scores must be interpreted with age. A score of 100 in a 40-year-old is dramatically more concerning than 100 in a 75-year-old.
| Age | Median CAC Score | 75th Percentile | Clinical Implication |
|---|---|---|---|
| 40-49 | 0 | 5 | Calcium rare; >100 very concerning |
| 50-59 | 0-10 | 60-100 | Calcium more common; scores >300 concerning |
| 60-69 | 20-30 | 200-300 | Wide range normal; context matters more |
| 70-79 | 50-100 | 500+ | Many have calcium; absolute burden still matters |
Your cardiologist references age-specific percentile charts to contextualize your score. A score that's above the 75th percentile for your age suggests more aggressive disease than one at the 50th percentile, even if the absolute numbers are identical.
Zero CAC Score and Longevity
A CAC score of 0 is associated with excellent long-term outcomes. Prospective studies following asymptomatic individuals with CAC=0 show:
- 10-year event rate: 1-3% (compared to 3-7% for age-matched population)
- Very few progress to significant disease within 5 years
- Cardiovascular mortality risk approaches general population averages
This makes CAC=0 one of the most reassuring findings in preventive cardiology. However, it's not license for complacency:
- Maintain LDL and ApoB in optimal ranges (LDL <100 mg/dL, ApoB <80 mg/dL ideally)
- Continue exercise, healthy diet, and stress management
- Monitor risk factors that can destabilize plaques (smoking, uncontrolled hypertension, diabetes)
- Rescreen every 5-10 years, more frequently if risk factors emerge
CAC Score vs. LDL Cholesterol
An important distinction: CAC scores measure existing plaque; LDL predicts future plaque. They provide complementary information.
- High LDL with CAC=0: You're at risk of developing coronary calcium; aggressive lipid management is crucial
- Low LDL with high CAC: You have existing disease; focus on plaque stabilization and risk factor control
- High LDL with high CAC: Immediate aggressive treatment needed
The strongest predictive marker is ApoB (apolipoprotein B), which counts the number of atherogenic particles regardless of their cholesterol content. Someone with LDL=160 but low ApoB (large particles) may have less risk than someone with LDL=140 but high ApoB (many small particles).
Key insight: Ideally, get both a CAC scan and ApoB testing. CAC tells you about existing atherosclerosis; ApoB predicts whether more is forming.
When NOT to Get a CAC Scan
CAC scans expose you to radiation and unnecessary cost in certain scenarios. You may not benefit from screening if:
- You're symptomatic: If you have chest pain or shortness of effort, cardiac catheterization or stress testing is more appropriate
- You're very young (<40) without major risk factors: The likelihood of significant CAC is extremely low
- You already have a diagnosis of coronary artery disease: CAC won't change management; you'd already be on appropriate therapy
- Your 10-year ASCVD risk is very low: Risk stratification with traditional factors may be sufficient
Discuss with your cardiologist whether CAC scanning adds meaningful information for your specific situation.
How Merios Helps
Merios contextualizes your CAC score alongside your lipid panel, including ApoB, triglycerides, and inflammation markers. Understanding whether your calcium burden is driven by high LDL, metabolic syndrome, or other factors helps prioritize interventions.
If you have a CAC score, upload your lipid panel to Merios. We'll show you how your cholesterol markers relate to your atherosclerosis burden and what targets matter most for slowing disease progression.
Upload your blood test to Merios →
This article is for educational purposes and does not replace medical advice. CAC scores should be interpreted by a cardiologist in the context of your complete risk profile, including age, family history, and additional testing. If you have a significant CAC score, consult a preventive cardiologist for personalized management recommendations. This information does not constitute medical diagnosis or treatment guidance.