A coronary artery calcium (CAC) score, also called an Agatston score, measures the amount of calcified plaque in the arteries that supply your heart, using a quick, non-contrast cardiac CT scan. It is reported in Agatston units (AU), and here the direction is simple: 0 is best, and a higher number means more calcified plaque and a higher risk of heart disease. A score of 0 means no detectable calcium, while scores climb through mild (1–99), moderate (100–399), severe (400–999) and extensive (1000 or more) tiers.
What is a coronary artery calcium score?
Coronary artery calcium scoring looks for calcium deposits inside the walls of your coronary arteries. Calcium builds up as part of atherosclerosis — the gradual hardening and narrowing of arteries — so its presence is a direct, physical marker that plaque has formed. Unlike a cholesterol number, which estimates risk, a CAC score shows disease that is actually there.
The test is a fast, non-contrast CT scan of the heart, usually taking only a few minutes and involving a low dose of radiation. A radiologist measures the area and density of calcium in each coronary artery and combines them into a single Agatston score in AU. Because it detects established plaque, CAC scoring is mainly used to refine cardiovascular risk in people who sit in an intermediate range — helping decide, for example, whether a statin is worthwhile. It complements, rather than replaces, other tools such as your ASCVD risk score and your cholesterol profile. You can see how it fits alongside other heart metrics on our Vitals & Imaging hub. Because this is an imaging result, the numbers below are a guide only — your cardiologist interprets them in the context of your full history.
Coronary artery calcium score normal range
The ideal CAC score is 0, meaning no calcified plaque was detected. As the score rises, so does the amount of plaque and the associated cardiovascular risk. The table below shows the standard Agatston tiers in Agatston units (AU).
| CAC score (AU) | Category | What it suggests |
|---|---|---|
| 0 | None (best) | No detectable calcified plaque |
| 1 – 99 | Mild | Small amount of plaque |
| 100 – 399 | Moderate | Moderate plaque burden |
| 400 – 999 | Severe | Extensive plaque |
| 1000 or more | Extensive | Very high plaque burden |
These bands follow the Agatston coronary artery calcium scoring method as used in ACC/AHA guidance. In Indian hospitals and diagnostic centres, CAC scoring is reported in the same Agatston units, so a result from a scan in India is directly comparable with these categories. The score is a snapshot of calcified plaque only; it does not capture softer, non-calcified plaque, which is why your doctor weighs it alongside your symptoms and other tests.
How CAC scores are interpreted by risk tier
Coronary calcium scoring does not use different "normal" numbers for men and women or for different ages the way many blood tests do — the tiers above apply to everyone. What changes is how a given score is interpreted in context. The table restates the severity tiers so you can locate your own result.
| Tier | CAC score (AU) | General interpretation |
|---|---|---|
| None | 0 | Very low likelihood of significant coronary disease |
| Mild | 1 – 99 | Some plaque present; modifiable risk worth addressing |
| Moderate | 100 – 399 | Clearly increased risk; often prompts preventive treatment |
| Severe | 400 – 999 | High plaque burden; aggressive prevention usually advised |
| Extensive | 1000+ | Very high burden; close cardiology follow-up |
Age and sex still matter to your doctor's reading of the number. Calcium tends to accumulate with age, so any calcium in a younger person is more notable, while a modest score in an older person is more common. Women often develop measurable calcium later than men. Because the raw score means different things at different ages, cardiologists sometimes also refer to a percentile — how your score compares with others of your age and sex — but the absolute Agatston number and its tier remain the core result. These are real modifiers of interpretation, not different numeric cut-offs, so the tiers above stay the same for everyone.
What a high coronary artery calcium score means
A higher CAC score means more calcified plaque has built up in your coronary arteries, and that is associated with a higher risk of future heart events such as heart attack. A moderate score (100–399) signals a clearly increased risk, and severe (400–999) or extensive (1000+) scores indicate a substantial plaque burden. The most common driver is long-standing atherosclerosis, influenced by factors such as high cholesterol, high blood pressure, diabetes, smoking, family history and age.
Importantly, a high calcium score is not the same as a blocked artery or an imminent heart attack, and it does not by itself say whether you have symptoms — it reflects the total amount of calcified plaque, not the degree of narrowing. Many people with a raised score feel completely well. What a high number does is move you into a group that benefits most from active prevention. Your cardiologist decides what, if anything, is needed next — which may include lifestyle changes, cholesterol-lowering treatment, or occasionally further testing if you have symptoms. Frame the result as useful information that helps you act early, not as a verdict.
What a coronary artery calcium score of zero means
Because 0 is the best possible result, a low or zero CAC score is reassuring. A score of 0 means no calcified plaque was detected and is linked with a very low short-term risk of coronary events; it is one of the strongest "negative" findings in preventive cardiology. For many people at intermediate risk, a zero score can support a shared decision to hold off on certain medications and focus on healthy habits.
A few caveats keep this in perspective. A zero score reflects calcified plaque only, so it does not completely rule out early, soft plaque that has not yet calcified — this matters more if you are a smoker, have diabetes or a strong family history, or already have symptoms. It is also a snapshot in time; calcium can develop later, which is why your doctor may suggest rechecking after some years. Even with a zero score, keep managing the basics like blood pressure, cholesterol and blood sugar.
How to improve your heart health and what to do
You cannot reverse the calcium that a scan detects — calcified plaque is essentially stable, hardened disease — but you can strongly influence whether more plaque forms and how your overall risk trends. Evidence-aligned steps include:
- Address cholesterol and blood pressure — work with your doctor on targets; medication such as a statin is often considered once calcium is present.
- Do not smoke — quitting is one of the most powerful ways to slow plaque progression.
- Stay physically active — regular aerobic activity such as brisk walking, cycling or swimming supports heart health.
- Eat a heart-friendly diet — plenty of vegetables, fruit, whole grains, pulses and healthy fats, with less salt, sugar and deep-fried food.
- Manage diabetes and weight — tight control of blood sugar and a healthy weight both lower cardiovascular risk.
In India, South Asian populations tend to face heart disease earlier and at lower body weights, so acting on risk factors promptly matters. Everyday habits — walking or cycling for transport, using stairs, home-cooked meals lower in fried and refined foods — are accessible and effective. When to see a doctor: discuss any CAC result with a doctor or cardiologist, especially a moderate or higher score, or any score paired with chest pain, breathlessness, palpitations or unusual fatigue. Seek urgent care for chest pain that is severe, spreading or comes with sweating or breathlessness. Tracking your heart numbers over time with ExaHealth — alongside vitals like your resting heart rate — helps you and your clinician see the bigger picture, not just one scan.
Guidelines and references
The scoring method and tiers in this article are based on established cardiology standards:
- American College of Cardiology (ACC) — ACC/AHA cardiovascular risk assessment and coronary calcium guidance: https://www.acc.org
- American Heart Association (AHA) — prevention and risk guidance: https://www.heart.org
Frequently asked questions
What is a good coronary artery calcium score?
A score of 0 is the best result, meaning no calcified plaque was detected and a very low short-term risk of coronary events. Lower is always better, and scores rise through mild (1-99), moderate (100-399), severe (400-999) and extensive (1000+) tiers.
Is a higher or lower calcium score better?
Lower is better. A coronary artery calcium score measures calcified plaque in your heart arteries, so 0 is ideal and higher numbers mean more plaque and higher cardiovascular risk.
What does a calcium score over 400 mean?
A score of 400 or above falls in the severe or extensive tier, indicating a high burden of calcified plaque and clearly increased cardiovascular risk. It usually prompts a cardiologist to advise aggressive prevention, though it is not the same as a blocked artery.
Can a coronary calcium score go back down?
No. Calcified plaque is stable, hardened disease, so the calcium a scan detects does not disappear. What you can influence is whether new plaque forms and your overall risk, through cholesterol and blood pressure control, not smoking, activity and a healthy diet.
Does a zero calcium score mean my heart is fine?
A zero score is very reassuring and links to low short-term risk, but it reflects calcified plaque only and does not fully rule out early soft plaque, especially if you smoke, have diabetes or a strong family history. Keep managing your risk factors and follow your doctor's advice on rechecking.
Is the CAC scan available in India?
Yes. Coronary artery calcium scoring is widely available at hospitals and diagnostic centres in India and is reported in the same Agatston units, so results are directly comparable with the standard tiers used worldwide.
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