A coronary artery calcium score can turn an invisible process inside the heart’s arteries into a single number. A result of 0 may sound reassuring, while a score of 100, 300 or 1,000 can understandably cause alarm.
The number is useful, but it is not a diagnosis on its own. It estimates how much calcified plaque is present in the coronary arteries—the blood vessels supplying the heart muscle. In general, a higher score means a larger burden of coronary atherosclerosis and a higher future risk of cardiovascular disease.
However, a calcium score does not show exactly how narrowed an artery is, cannot detect all soft plaque and does not predict precisely if or when a heart attack will happen. Its main value is helping a clinician understand risk and make more informed decisions about prevention.
This guide provides general information about coronary artery calcium results. A score should be interpreted by an appropriately qualified clinician alongside your symptoms, age, blood pressure, cholesterol, medical history and other cardiovascular risk factors.
What is a coronary artery calcium score?
A coronary artery calcium score—often shortened to a CAC score—is calculated from a specialised CT scan of the heart. The scan looks for calcium within plaque in the walls of the coronary arteries.
Coronary plaque develops through a process called atherosclerosis. It contains varying amounts of fat, cholesterol, inflammatory material, fibrous tissue and calcium. As plaque develops and changes over time, some of it can become calcified and visible on CT imaging.
The result is usually reported as an Agatston score, named after one of the doctors involved in developing the method. The calculation considers the area and density of calcium seen in the coronary arteries and combines the findings into one total score.
A higher score indicates a greater overall amount of calcified coronary plaque. It does not simply measure the calcium you have consumed in food, and a high score is not caused by drinking milk or taking a normal dietary amount of calcium.
The British Heart Foundation describes CT calcium scoring as a simpler form of heart CT that measures calcified or hardened plaque rather than providing detailed pictures of the coronary arteries.
What do the calcium score ranges mean?
Calcium score categories vary slightly between reports and clinical guidelines. A commonly used interpretation is:
| Agatston calcium score | Common description | General interpretation |
|---|---|---|
| 0 | No detectable coronary calcium | No calcified plaque was identified |
| 1–99 | Mild calcification | A small amount of calcified coronary plaque is present |
| 100–299 | Moderate calcification | A definite and more substantial plaque burden is present |
| 300 or above | Moderate to severe or severe calcification | A high burden of coronary atherosclerosis is present |
Some reports use 400 rather than 300 as the threshold for severe calcification. You may therefore see scores of 300 to 399 described differently by different providers. This is not necessarily a contradiction; it reflects variation in the categories used.
The precise number should not be interpreted as a sharp dividing line between safety and danger. A score of 101 is not fundamentally different from a score of 99, even though it moves into another reporting category.
What matters is the overall pattern: whether calcium is absent, mildly present, clearly established or extensive—and what that finding means in the context of the individual being tested.
What does a calcium score of 0 mean?
A score of 0 means the scan did not detect calcified plaque in the coronary arteries. In an asymptomatic adult for whom calcium scoring is appropriate, this is generally associated with a low risk of a coronary event over the following years.
However, a zero score is not the same as a guarantee of healthy coronary arteries. Plaque can exist before it becomes calcified. This non-calcified or “soft” plaque may not be visible on a calcium-scoring scan.
This limitation is particularly relevant in younger people, because atherosclerosis may be at an earlier, non-calcified stage. A younger person can have important risk factors or even coronary disease despite having little or no detectable calcium.
A score of 0 also does not cancel out major risk factors such as:
- current smoking;
- diabetes;
- very high cholesterol or familial hypercholesterolaemia;
- a strong family history of premature coronary disease;
- significant high blood pressure;
- symptoms suggestive of angina.
Some international guidelines use a zero score to support postponing statin treatment in selected people whose treatment decision is genuinely uncertain. Exceptions commonly include smokers, people with diabetes and those with a strong family history or very high cholesterol.
In the UK, cardiovascular prevention decisions usually begin with an overall risk assessment rather than the calcium score alone. A clinician should review the result rather than advising you to stop or avoid medication purely because the number is zero.
What does a score of 1 to 99 mean?
A score between 1 and 99 confirms that some calcified coronary plaque is present. Even a small positive score is evidence of coronary atherosclerosis, although the amount is usually described as mild.
The significance depends heavily on age. A score of 20 in a 40-year-old may be more unusual and concerning for lifetime risk than the same score in a person in their seventies. This is why a positive result should not be dismissed simply because the absolute number is below 100.
A mild score does not tell the doctor whether an artery has a significant narrowing. Calcified plaque may be spread through the artery wall without severely restricting blood flow. Conversely, a relatively low score cannot exclude a clinically important area of non-calcified plaque.
The result may prompt a closer review of cholesterol, blood pressure, smoking, diabetes risk, diet, exercise and family history. Depending on the complete risk profile, a clinician may discuss cholesterol-lowering medication.
Our guide to understanding cholesterol test results explains the difference between total cholesterol, LDL, HDL, triglycerides and non-HDL cholesterol.
What does a score of 100 to 299 mean?
A score of 100 to 299 is commonly described as moderate coronary calcification. It indicates a definite burden of coronary atherosclerosis and is associated with a higher future cardiovascular risk than a score below 100.
This result usually deserves a structured clinical review even if the person feels well. The clinician will consider whether treatment of cholesterol, blood pressure or other risk factors should be started or intensified.
A score above 100 often has greater influence on treatment decisions in international prevention guidance. However, this does not mean every person with a score of 100 receives an identical prescription. Age, cholesterol, blood pressure, diabetes, smoking and previous cardiovascular disease remain important.
The score still does not establish the degree of blockage. A person can have a moderate total calcium burden without one critical narrowing, while another may have symptoms requiring a more detailed test.
If the scan was arranged privately, make sure the result reaches your NHS GP. A numerical report without a plan can leave important questions unresolved, particularly if blood tests and blood pressure have not recently been checked.
What does a score of 300, 400 or more mean?
A score of 300 or more indicates a high overall burden of calcified plaque. Some reporting systems use 400 as the start of the severe category, but either result represents substantial coronary atherosclerosis and a significantly increased level of cardiovascular risk.
Very high results can extend into four figures. A score above 1,000 reflects extensive calcification and is generally associated with particularly high long-term risk. It should lead to timely medical review and active management of modifiable risk factors.
A high score does not mean that a heart attack is inevitable or about to happen. Many people with substantial calcium remain well, especially when risk factors are identified and treated. The result is best viewed as a strong warning to take prevention seriously.
It is equally important not to assume that a higher number reveals where an artery is narrowed. The total score measures plaque burden across the coronary arteries. It does not directly assess blood flow or show the inside of each artery in the same way as CT coronary angiography or invasive angiography.
Whether further investigation is needed depends mainly on symptoms, clinical history and the scan report—not simply on reaching a particular numerical threshold.
Why do age, sex and percentile matter?
Coronary calcium generally becomes more common with age. Men also tend to develop detectable calcium earlier than women, although cardiovascular disease remains an important risk for both.
A percentile places your score in context by comparing it with scores in people of a similar age and sex, and sometimes ethnicity. Being in the 75th percentile means your calcium burden is greater than that of approximately 75% of the relevant reference group.
For example, an absolute score of 50 may be relatively unusual in a young adult but fairly common at an older age. The younger person may therefore have a much higher percentile despite both people having the same Agatston score.
The Multi-Ethnic Study of Atherosclerosis reference tool can estimate percentiles using age, sex and ethnicity. It is a population comparison tool, not a diagnosis or personal treatment recommendation.
Absolute score and percentile answer different questions:
- The absolute score estimates the total burden of calcified plaque and is strongly related to the risk of cardiovascular events.
- The percentile indicates whether that burden is high or low compared with similar people.
Clinicians may consider both. A high percentile can be particularly informative when a younger person has a modest but unexpectedly early amount of coronary calcium.
What can and cannot be learned from the score?
The calcium score is useful because it provides direct evidence of calcified coronary atherosclerosis. Traditional risk calculations estimate the likelihood of future disease from factors such as age, cholesterol, blood pressure and smoking. CAC scoring shows whether one visible marker of coronary plaque is already present.
It can help refine risk when the decision about preventative treatment remains uncertain. For some people, a score of 0 may support a less intensive approach. For others, an unexpectedly positive or high result may make the benefit of treatment clearer.
What the score cannot reliably tell you is:
- whether a particular artery has a severe narrowing;
- whether chest pain is coming from the heart;
- how much non-calcified plaque is present;
- whether a heart attack will occur;
- when a cardiovascular event might happen;
- whether a stent or bypass operation is needed.
Calcification usually represents the overall burden of atherosclerosis more than the danger of one individual plaque. A highly calcified plaque is not necessarily the plaque most likely to rupture.
The result may also include scores for individual arteries, such as the left anterior descending, right coronary and circumflex arteries. These add detail but still require interpretation as part of the overall report.
How is calcium scoring different from CT coronary angiography?
Both tests use CT imaging, but they answer different questions.
A dedicated calcium-scoring scan is usually quick and does not require an injection of contrast dye. It detects and measures calcified plaque, producing the CAC number.
CT coronary angiography—often written as CTCA—uses intravenous contrast to provide more detailed images of the coronary arteries. It can show the artery lumen, areas of narrowing and both calcified and non-calcified plaque.
A CAC scan is mainly a tool for refining future risk in appropriately selected people who do not have symptoms. CTCA is more likely to be used when a clinician is investigating possible coronary artery disease, including certain presentations of chest pain.
The British Heart Foundation notes that calcium scoring does not provide the detailed arterial pictures produced by CT coronary angiography. For a general explanation of CT technology, contrast and radiation, see our guide to what a CT scan shows and how it differs from MRI.
Someone with chest pain should not choose a calcium-scoring package as a substitute for medical assessment. A zero result cannot safely rule out every cardiac cause of symptoms.
What happens after an abnormal calcium score?
An abnormal score does not usually mean that an operation or stent is needed. The first step is commonly a comprehensive cardiovascular review.
This may include checking:
- blood pressure;
- a full lipid profile;
- diabetes risk or HbA1c;
- smoking status;
- family history of premature heart disease;
- diet, weight and physical activity;
- any chest discomfort, breathlessness or reduced exercise tolerance.
Treatment focuses on reducing the chance that coronary disease will progress or cause an event. Depending on the person’s overall risk, this may involve a statin or adjustment of existing cholesterol medication, treatment for high blood pressure, diabetes management and support to stop smoking.
Our guides to statins, their benefits and side effects and high blood pressure explain two common parts of cardiovascular prevention.
Do not begin aspirin because of a calcium score without medical advice. Aspirin can reduce clotting but also increases the risk of bleeding. Whether it is appropriate depends on a careful balance of cardiovascular and bleeding risks.
Further tests may be considered when symptoms or other findings suggest they are needed. A high score alone does not automatically require an exercise test, CT coronary angiogram or invasive coronary angiogram.
Can lifestyle changes or statins lower the calcium score?
The aim of treatment is to reduce cardiovascular events, not necessarily to make the calcium number fall. Established coronary calcium usually does not disappear, even when risk is being managed effectively.
Statins lower LDL cholesterol and reduce the risk of heart attack and stroke in appropriate patients. They can also change the composition of plaque, helping make it more stable. In some circumstances, calcification may continue or even become denser while the plaque becomes less likely to rupture.
This is one reason repeat calcium scans are not generally used to judge whether a statin is working. A rising number does not automatically mean that treatment has failed, and a repeat result may not change management.
Progress is more often monitored through cholesterol results, blood pressure, diabetes control, smoking status and adherence to treatment.
Useful lifestyle measures include stopping smoking, being physically active, eating a balanced diet rich in vegetables, fruit and fibre, moderating saturated fat, maintaining an appropriate weight and controlling blood pressure. These steps cannot erase a score, but they can materially reduce future risk.
Our detailed guide to reducing the risk of heart attack and stroke covers practical preventative measures in more detail.
Who might benefit from a calcium-scoring scan?
CAC scoring is most useful when someone does not have cardiac symptoms and their level of cardiovascular risk—or the decision about preventative medication—remains uncertain after a standard assessment.
It may be discussed when there is a strong family history of premature coronary disease, borderline cholesterol or several moderate risk factors that do not lead to an obvious treatment decision.
It is less likely to add useful information when a person is already known to have coronary heart disease, has had a heart attack, stent or bypass operation, or clearly requires preventative treatment because of established high risk.
The test may also be less informative in very young adults, in whom plaque is more likely to be non-calcified. It involves a small dose of ionising radiation and should not be undertaken casually or repeated without a clinical reason.
In the UK, routine primary-prevention decisions are generally based on an overall cardiovascular risk assessment. NICE guidance on cardiovascular disease risk assessment and reduction should be considered alongside individual clinical judgement.
If you are thinking about paying for cardiac testing, our guide to private cardiology tests, consultations and insurance cover explains common services and the extra costs that may arise.
When should chest symptoms be treated as urgent?
A calcium score is designed mainly to assess future risk. It should not be used to self-assess new or worsening chest symptoms.
Call 999 if you have sudden chest pain or pressure that does not go away, particularly if it spreads to the arm, jaw, back or stomach, or is accompanied by sweating, breathlessness, nausea, dizziness or a feeling of impending doom.
Symptoms can be less typical in women, older adults and people with diabetes. Severe breathlessness, collapse or sudden marked weakness also requires urgent assessment.
Do not be falsely reassured by a previous score of 0. Non-calcified plaque, coronary spasm and other heart conditions can cause serious symptoms without a high calcium score.
For more information about common and urgent causes, read our guide to chest pain and when to seek help. The NHS also explains how coronary heart disease is assessed and diagnosed.
Frequently asked questions
Is a calcium score of 0 good?
It is generally reassuring and means that no calcified coronary plaque was detected. In an appropriate asymptomatic patient, it is associated with a low short-term risk. It does not exclude non-calcified plaque or override serious risk factors and symptoms.
Is any coronary calcium normal?
Calcium becomes more common with age, but any score above 0 indicates detectable calcified coronary plaque. Whether the amount is unusually high depends partly on age, sex and the person’s wider risk profile.
Is a calcium score of 100 high?
A score of 100 marks the beginning of the range commonly described as moderate calcification. It confirms a meaningful burden of coronary atherosclerosis and usually warrants a careful review of cardiovascular risk and prevention.
Is a score above 400 dangerous?
A score above 400 indicates extensive calcified plaque and a high level of long-term cardiovascular risk. It does not mean a heart attack is imminent, but it deserves timely medical review and active risk-factor management.
Can you have blocked arteries with a calcium score of 0?
Yes. A calcium scan does not identify non-calcified plaque, which may sometimes cause significant narrowing. A zero score is therefore not a reliable way to rule out coronary disease in someone with suspicious symptoms.
Does a high score mean I need a stent?
No. The score measures total calcified plaque rather than the severity of a specific blockage. A stent is considered according to symptoms, detailed imaging, blood-flow effects and clinical circumstances—not from the calcium score alone.
Can the calcium score go down?
Established calcium usually does not disappear. Effective prevention can reduce the risk of plaque progression or rupture without lowering the score. Treatment success is not judged simply by repeating the scan.
Should I take a statin after a positive calcium score?
A positive result may strengthen the case for a statin, especially when the score is 100 or more or unusually high for age. The decision should be made with a clinician after considering cholesterol, blood pressure, smoking, diabetes, family history and potential treatment benefits.
Should I take aspirin for a high calcium score?
Not without medical advice. Aspirin may cause serious bleeding, and its role in preventing a first cardiovascular event is limited to selected patients after an individual assessment.
How often should a calcium scan be repeated?
There is no routine interval suitable for everyone. A repeat scan may occasionally be considered after several years when an initial score was 0 and the result would affect management. Repeating an already positive score often adds little because the presence of coronary plaque is already established.
Can calcium scoring detect a previous heart attack?
Not reliably. The test measures calcified coronary plaque rather than damage to the heart muscle. An ECG, echocardiogram, cardiac MRI or other investigation may be needed when a previous heart attack is suspected.
