The Journal

What your blood tests actually mean

Most testing sites hand you numbers. We explain them: what each marker measures, why it matters, when to test and what to do next. Plain English, grounded in the evidence, and honest about what a test cannot tell you.

Guides · Latest

The PSA test: what it can and cannot tell you

PSA is the main blood test we have for prostate cancer, and it is genuinely useful. It is also imprecise in both directions. Knowing that before you test is the difference between a number that helps and a number that frightens you.

8 min read · 29 Jul 2026

Heart & circulation

Cholesterol, apoB, lipoprotein(a) and the markers behind heart risk.

Heart health tests

Heart & circulation

apoB: the cholesterol number that actually matters

A standard cholesterol test weighs the cargo. apoB counts the delivery trucks, and the number of trucks tells you more about what ends up in your artery walls than the cargo does.

6 min read · 7 Jul 2026

Metabolic health

Blood sugar, HbA1c, weight and the slow changes that come first.

Longevity & prevention tests

Metabolic health

HbA1c: your blood sugar, averaged over three months

A finger-prick glucose is a single snapshot, high after lunch, low before breakfast. For most people HbA1c is the running average of your blood sugar over about three months, which is why it's the number used to judge diabetes risk.

5 min read · 6 Jul 2026

Not sure which test you need?

Every product page says what is measured, who it is for and who it is not for, before you buy. Or describe what you want to understand and Max, our test finder, points you at the panels that measure it.

Browse all tests