A CT calcium score is a quick, noninvasive heart scan that measures the amount of calcified plaque in your coronary arteries. The result is a single number that estimates your risk of having a heart attack or other cardiovascular event over the next decade. The scan takes about 10 to 15 minutes, uses no contrast dye, and delivers a low dose of radiation.
What the Scan Actually Measures
Over time, cholesterol and fat can build up inside the walls of the arteries that supply blood to your heart. As these deposits age, calcium collects in them, hardening the plaque. A CT calcium scan detects those calcium deposits using a specialized, fast CT scanner that captures images of your heart between beats. The resulting number, called an Agatston score, reflects how much calcified plaque is present across all your coronary arteries.
This is different from a coronary CT angiogram (CCTA), which uses contrast dye and higher radiation to produce detailed images of the inside of your arteries. A CCTA can show whether an artery is actually narrowed or blocked and reveal soft plaque that hasn’t calcified yet. A calcium score, by contrast, doesn’t visualize the artery opening at all. It simply quantifies how much hardened plaque exists, which serves as a reliable marker of overall coronary artery disease burden.
What Your Score Means
A score of zero means no detectable calcified plaque was found. For most people, this is reassuring: it signals low short-term risk, and cholesterol-lowering medication can often be deferred unless other significant risk factors are present (such as diabetes, very high LDL cholesterol, smoking, or a strong family history of early heart disease). A zero score doesn’t guarantee you’ll never develop heart disease, so repeat scanning may be recommended in 3 to 7 years depending on your baseline risk level.
Scores between 1 and 99 indicate mild plaque buildup. At this stage, statin therapy is typically recommended to bring LDL cholesterol below 100 mg/dL. Scores of 100 to 299 reflect moderate atherosclerosis and both short-term and lifetime risk climb meaningfully. More aggressive cholesterol lowering, targeting LDL below 70 mg/dL, is generally advised. Aspirin also enters the picture once scores reach 100 or higher, as the benefit of preventing clots begins to outweigh the bleeding risk at that threshold. Scores above 1,000 carry the highest risk and call for the most intensive treatment, with an LDL goal below 55 mg/dL.
Data from large population studies bear this out. Compared to people with no coronary calcium, those with high calcium burdens face a 3.3 to 5.6 times greater risk of a coronary event over roughly 12 years of follow-up. The 10-year rate of cardiovascular events stays below 5% in the zero-calcium group but rises above 13% in the high-calcium group.
Who Should Get the Test
Calcium scoring is most useful for people who fall into the gray zone of heart disease risk. If a standard risk calculator puts your 10-year chance of a cardiovascular event between 5% and 20%, the scan can tip the decision about whether to start medication. The 2019 ACC/AHA prevention guideline gives calcium scoring a strong recommendation (Class IIa) for exactly this scenario: when a formal risk estimate has been done but the treatment decision still feels uncertain to you or your doctor. A 2022 expert consensus pathway reinforced this, specifically noting the test’s value when there’s either clinician uncertainty or patient hesitancy about beginning statin therapy.
The test is also considered for people under 5% estimated risk if they have a family history of premature heart disease, since standard calculators can underestimate risk in that group.
When It’s Not Helpful
If you already have symptoms like chest pain or shortness of breath with exertion, calcium scoring isn’t the right test. You need imaging that can show whether an artery is actually blocked, not just calcified. Similarly, if you’re already high risk, say you have diabetes or very high cholesterol, guidelines already recommend treatment regardless of your calcium score. The scan wouldn’t change your management, so it adds cost and radiation without benefit.
Young adults are also poor candidates. Calcification typically begins developing in the fifth decade of life, so a scan in your 20s or 30s would likely come back at zero even if early, non-calcified plaque were forming. You’d be exposed to radiation without gaining useful information.
What to Expect During the Scan
Preparation is minimal. You’ll need to avoid food, drink, caffeine, and tobacco for about four hours beforehand. No contrast dye is injected, which means no IV line and no risk of dye-related side effects. You lie on a table that slides into the CT scanner, electrodes are placed on your chest to sync the images to your heartbeat, and you hold your breath for a few seconds while the scanner captures the images. The actual scanning takes only a few minutes. From check-in to walking out, the whole visit runs about 10 to 15 minutes.
Radiation Exposure
The recommended radiation dose for a calcium score scan averages 1.0 to 1.5 millisieverts (mSv) and should not exceed 3.0 mSv. For comparison, a standard chest X-ray delivers about 0.1 mSv, and natural background radiation in the U.S. totals roughly 3 mSv per year. So the scan is equivalent to a few months of everyday background exposure. That said, real-world doses vary by facility. Studies have found actual doses ranging from 0.8 to 10.5 mSv across different centers, which is a wide spread. Asking your imaging center about their typical dose is reasonable.
Cost and Insurance Coverage
Nearly all insurance payers, including Medicare, currently deny coverage for calcium scoring when it’s used as a preventive screening tool. This is a point of ongoing debate in cardiology, given the strength of evidence supporting the test. The practical result is that most people pay out of pocket. The good news is that many hospitals and imaging centers have dropped their price for the scan to the $50 to $100 range, making it one of the more affordable cardiac tests available. Prices outside that range do exist, so it’s worth calling ahead to compare costs at facilities near you.