Coronary calcium score
A coronary artery calcium (CAC) score is a quick CT scan that shows whether hardened plaque has already formed in the arteries of your heart. It is a strong predictor of heart attack risk and a good tie-breaker when you can't decide about a statin. A score of zero buys only a few years, and no randomised trial has yet shown that getting scanned leads to fewer heart attacks or deaths.
Consider a calcium scan only if your estimated 10-year risk is intermediate, or in some cases borderline, and you are unsure about starting a statin — in men from 40 and women from 45. Any calcium means plaque is there and is a reason to treat; a zero lets some people put off a statin, with a rescan in 3 to 7 years.
What the scan does
The scan is a non-contrast computed tomography (CT) measurement of calcium in the walls of the coronary arteries. It turns a probability into anatomy: a risk calculator says how likely people like you are to have a heart attack or stroke, while measurable coronary calcium means you already have plaque that isn't yet causing symptoms, so you're no longer in a statistical grey zone.
US guidelines estimate 10-year risk with a calculator called PREVENT.[1] For adults at intermediate (5% to under 10%) or selected borderline (3% to under 5%) 10-year risk whose treatment decision is still uncertain, the 2026 US cholesterol guideline (from the American College of Cardiology and American Heart Association) recommends a calcium scan as a selective tool, in men from age 40 and women from 45.[2] It is not a routine test for everyone.
What the score means
The guideline sets an LDL cholesterol (LDL-C) goal by score:[3]
| Calcium score | What it means | LDL-C goal |
|---|---|---|
| 0 | No calcified plaque; low near-term risk, but the "warranty" lasts only about 3–7 years | None; deferring a statin and rescanning in 3–7 years is reasonable only in the situation below |
| 1–99, and below the 75th percentile for age, sex and race | Definite but mild disease | <100 mg/dL (2.6 mmol/L) |
| 100–299, or at or above the 75th percentile with a score below 300 | Moderate plaque burden | <70 mg/dL (1.8 mmol/L) |
| 300–999 | Severe plaque burden | <70 mg/dL (1.8 mmol/L); intensifying to <55 mg/dL (1.4 mmol/L) is reasonable |
| ≥1,000 | Extensive plaque burden | <55 mg/dL (1.4 mmol/L) |
Any detectable calcium is a reason to start cholesterol-lowering treatment, particularly at a score of 100 or more or at or above the 75th percentile for your age, sex and race.
In a retrospective, observational study of 13,644 adults scanned at a US military hospital (average age 50, mostly men), statin users with a zero score did no better than non-users over about 10 years, while among those with a score above 100, treating about 12 people for a decade prevented one heart attack, stroke or cardiovascular death. Healthier habits among statin takers may explain part of that gap.[4]
A zero buys time, but less than often claimed
In a large multi-ethnic US study (the Multi-Ethnic Study of Atherosclerosis), about half of people who started with a zero score had some calcium within 10 years. The estimated "warranty period" ran about 3 to 7 years depending on sex and ethnicity, and diabetes shortened it by 35–38%, to about 3 years in men and 4 in women. About one in five of the coronary events people with an initial zero had over that decade struck before a repeat scan at 3–5 years.[5]
So the guideline treats putting off a statin on a zero score as reasonable only for adults at intermediate (or selected borderline) risk who prefer to avoid medication and who have none of these higher-risk conditions:[6]
- familial hypercholesterolemia (an inherited cause of very high LDL) or an LDL-C of 190 mg/dL (4.9 mmol/L) or more;
- diabetes after age 40;
- current smoking;
- a strong family history of premature heart disease.
Even then, it advises a repeat scan in 3 to 7 years.
What it hasn't shown
The calcium score is a strong predictor of risk. Whether getting scanned improves outcomes is a different question, and the evidence is weak: in randomised trials so far, scanning modestly improved some risk factors, mainly cholesterol, and may have helped people keep taking their statins, but none has shown fewer heart attacks or deaths. LDL-C fell only slightly more than with usual care, by about 0.13–0.16 mmol/L (5–6 mg/dL), and the three studies that tracked heart events or deaths were limited mainly by few events, short follow-up or small samples.[7]
What to do
- Use it to break a tie, not as a screen: only when your 10-year risk is intermediate (or, in some cases, borderline) and the statin decision is genuinely uncertain.
- If the score is above zero, treat it as a reason to lower LDL cholesterol, to the goal in the table.
- If it is zero and you have none of the higher-risk conditions above, deferring a statin is reasonable; rescan in 3 to 7 years. With diabetes, smoking, very high LDL cholesterol or a strong family history, a zero is not a reason to wait.
- Read it alongside the rest — apolipoprotein B (apoB), Lp(a) and the long-run LDL trajectory; see Lipid management.
Further reading
- Blumenthal RS et al. 2026 ACC/AHA/Multisociety guideline on the management of dyslipidemia. J Am Coll Cardiol 2026;87:2624.[8]
- Dzaye O et al. Warranty Period of a Calcium Score of Zero: Comprehensive Analysis From MESA. JACC Cardiovasc Imaging 2021.[9]
- Scheu V et al. Coronary atherosclerosis screening in asymptomatic adults using coronary artery calcium for cardiovascular prevention: a systematic review of randomised controlled trials and prospective cohorts. BMJ Open 2025.[10]