How healthy are my blood vessels / what is my vascular age?
For a first impression of your vascular health, an ApoB blood test is the simplest and most accessible step; a CAC scan adds the most value when your risk remains unclear after blood testing.
ApoB and a CAC score each measure a different aspect of your cardiovascular health, and together they provide a reasonably complete picture. ApoB counts the number of harmful lipid particles in your blood. This is comparable to LDL cholesterol, but more accurate when your triglycerides are elevated or your LDL value is borderline. It involves a standard blood draw, with virtually no risk, and you can request it from your GP as part of a lipid panel.
A CAC score goes one step further: through a CT scan, it shows how much calcified plaque is actually present in your coronary arteries. A higher score means more plaque and more risk. A score of zero offers some reassurance, but does not rule anything out completely, because the scan only detects calcified plaque, not the softer variety. The test is most useful when your risk has already been assessed as 'intermediate' and the result has a concrete influence on treatment decisions. When risk is already very low or very high, it adds little value.
In practical terms, ApoB is the logical first step: inexpensive, radiation-free, and informative for everyone. The CAC scan is a follow-up step if your cardiovascular risk remains unclear after blood testing. That decision is best discussed with your GP or cardiologist. Bear in mind that the scan does involve a small radiation dose and sometimes produces incidental findings that can lead to additional investigations -- something worth knowing before you request it.