Coronary calcium score results: what your CAC means
A coronary artery calcium (CAC) scan is a short CT scan of the heart that counts hardened, calcified plaque in the heart arteries. The result is a number, the Agatston score. A score of 0 means no calcium was seen; higher numbers mean more. It is one part of your heart risk picture, not a complete answer, and your doctor decides what it means for you. (RadiologyInfo, 2026) (CAC-DRS primer, 2023)
A calcium score is for people without symptoms. If you have chest discomfort, shortness of breath, or pain in the arms, back, neck, jaw or upper stomach, call 911, even if you are not sure it is a heart attack. (MedlinePlus)
What the score bands mean
The USPSTF notes that scoring systems and cut-offs vary, but the usual point of comparison is a score of 0. (USPSTF, 2018) Two common ways to group the score are below. Your report may use either one.
| CAC-DRS category | Score | Risk label |
|---|---|---|
| CAC-DRS 0 | 0 | Very low |
| CAC-DRS 1 | 1 to 99 | Mild |
| CAC-DRS 2 | 100 to 299 | Moderate |
| CAC-DRS 3 | 300 or more | Moderate to severe |
Source for the categories: the CAC-DRS reporting system as set out in a 2023 primer, with the top group (CAC 300 or more) as defined in the CAC Consortium validation study. (CAC-DRS primer, 2023) (CAC Consortium, 2020) Where they differ: RadiologyInfo, the patient site of the American College of Radiology and RSNA, uses five bands: 0 no evidence of coronary artery disease, 1 to 10 minimal, 11 to 100 mild, 101 to 400 moderate, and over 400 extensive. (RadiologyInfo, 2026)
The score predicts heart attack and stroke in a graded way: the higher the score, the higher the risk, and this holds apart from other risk factors such as age, sex and ethnicity. (ACC/AHA, 2018) The ACC/AHA guideline names a score of 100 or more, or one at or above the 75th percentile for age, sex and race, as the point where the scan moves risk upward. (ACC/AHA, 2019)
What a score of 0 means, and how long it lasts
- A zero identifies people at lower risk of heart attack, stroke and death over more than 10 years. (ACC/AHA, 2019) RadiologyInfo puts the chance of a heart attack over the next two to five years as very low. (RadiologyInfo, 2026)
- It does not rule out soft plaque that has not calcified. (ACC/AHA, 2019) RadiologyInfo notes that in people under 50, coronary artery disease can be present without calcium. (RadiologyInfo, 2026)
- The ACC/AHA guideline says a zero should not be read as low risk in people who keep smoking, have diabetes or a family history of heart disease, or possibly have a chronic inflammatory condition. (ACC/AHA, 2019)
- How long it holds: after a zero, the guideline suggests reassessing in 5 to 10 years. (ACC/AHA, 2019) The 2018 cholesterol guideline adds that when, or whether, to repeat the scan after a zero is still uncertain. (ACC/AHA, 2018)
A score of 1 to 99
Some calcium is present. The 2019 ACC/AHA guideline gives 10-year rates of heart attack or stroke of 3.8%, 6.5% and 8.3% for people with a score of 1 to 99 aged 45 to 54, 55 to 64 and 65 to 74, and calls the change in risk from this band modest. It suggests repeating the risk discussion with your doctor. (ACC/AHA, 2019)
Your percentile
Many reports also give a percentile. It compares your score with people of the same age, sex and race or ethnicity in the MESA study; the MESA calculator covers ages 45 to 84 and four groups (Black, Chinese, Hispanic and White). (MESA) A score at the 75th percentile or above is one of the points the ACC/AHA guideline uses to move risk upward, even if the score itself is under 100. (ACC/AHA, 2019)
Who the scan is meant for
| Source | What it says |
|---|---|
| ACC/AHA 2019 and 2018 | Reasonable for adults whose estimated 10-year risk is intermediate (7.5% to under 20%), or selected adults at borderline risk (5% to under 7.5%), when a prevention decision is still uncertain. An option from age 40. Not recommended routinely for people at lower risk. (ACC/AHA, 2019) (ACC/AHA, 2018) |
| USPSTF 2018 | Evidence insufficient (I statement) to add a calcium score to the usual heart risk estimate in adults without symptoms. Update in progress. (USPSTF, 2018) |
| UK (NICE) and Europe (ESC) | Their usual risk tools, QRISK3 and SCORE, do not include a calcium score, as summarized by the USPSTF. (USPSTF, 2018) |
Where they differ: the ACC/AHA uses the score to settle unclear cases, while the USPSTF found that adding it improves risk prediction a little but found no good evidence that care guided by it leads to fewer heart attacks or deaths. (ACC/AHA, 2019) (USPSTF, 2018) RadiologyInfo notes that not all insurance plans cover the scan. (RadiologyInfo, 2026) For the other heart screenings by age, see heart screenings by age.
Radiation and incidental findings
- Radiation: the USPSTF gives a dose of 0.4 to 2.1 mSv, which it calls relatively low. (USPSTF, 2018) The ACC/AHA advises having it done where current technology gives the lowest radiation possible. (ACC/AHA, 2019) Tell the staff if you could be pregnant. (RadiologyInfo, 2026)
- Incidental findings: the scan also shows part of the lungs. A review of 7 studies found incidental findings, such as lung nodules, on 8% to 58% of scans, and these can lead to more tests and procedures. (USPSTF, 2018)
- What it does not show: the score measures hardened plaque only. It does not show softer plaque or whether an artery is narrowed. A high score may be followed by other heart tests, which may or may not add useful information. (RadiologyInfo, 2026)
Is it a yearly test?
No. After a zero, the ACC/AHA suggests reassessing in 5 to 10 years; for a score of 1 to 99 in someone not treated, it says a repeat scan in 5 years may have some value but data are limited. (ACC/AHA, 2019) The CAC-DRS primer quotes the SCCT expert consensus: when a change would alter care, a repeat may be considered at about 5 years after a zero and 3 to 5 years after a score above zero. (CAC-DRS primer, 2023) If calcium is found on a lung cancer screening CT, see lung cancer screening results.
Questions people ask
What does a coronary calcium score of 0 mean?
No calcified plaque was seen in the heart arteries. The 2019 ACC/AHA guideline says a zero identifies people at lower risk of heart attack, stroke and death over more than 10 years. It does not rule out soft plaque that has not calcified, and the guideline says not to treat a zero as low risk in people who smoke, have diabetes or a family history of heart disease. (ACC/AHA, 2019)
Is a calcium score of 100 bad?
It means more calcified plaque. The ACC/AHA guideline names a score of 100 or more, or a score at or above the 75th percentile for your age, sex and race, as the point where the scan reclassifies risk upward. What that means for you is a decision you make with your doctor. (ACC/AHA, 2019)
What is a CAC percentile?
It compares your score with people of the same age, sex and race or ethnicity in the MESA study. The MESA calculator covers ages 45 to 84. A 75th percentile score means your score is higher than that of 75 in 100 similar people. (MESA) (ACC/AHA, 2019)
Does the USPSTF recommend a coronary calcium scan?
No grade either way. In 2018 it found the evidence insufficient (I statement) to add a calcium score to the usual heart risk estimate in adults without symptoms. Its website lists an update in progress for calcium scoring. (USPSTF, 2018)
How often should a calcium score be repeated?
It is not a yearly test. After a zero, the ACC/AHA guideline suggests reassessing in 5 to 10 years. The CAC-DRS primer quotes the SCCT expert consensus: a repeat scan may be considered after about 5 years for a zero and 3 to 5 years for a score above zero, when the result would change care. (ACC/AHA, 2019) (CAC-DRS primer, 2023)