Psa
Prostate-specific antigen, a protein made by the prostate. Used as a screening and monitoring marker for prostate conditions in men.
Typical reference range
| Range | Unit |
|---|---|
| 0–4 | ug/l |
What Psa measures
PSA (prostate-specific antigen) is a protein made by the prostate gland. A small amount naturally leaks into the blood, where a PSA test can measure it. It is used as one input in assessing prostate health and in screening for prostate problems. Importantly, a PSA test is not a cancer test on its own: many non-cancer conditions can raise it, and a result is always interpreted in context rather than read as a diagnosis. Whether to screen with PSA at all is an individual decision, best made together with a clinician, because there is genuine debate about the balance of benefits and harms of routine screening. A clinician weighs your age, symptoms, family history, and preferences when deciding whether and how often to test.
What a high Psa can mean
A high PSA result does not mean cancer. Many everyday and non-cancer causes can raise PSA, and they are common. Causes frequently associated with a higher reading include:
- an enlarged prostate (benign prostatic hyperplasia, or BPH), which is very common with age
- prostatitis (inflammation or infection of the prostate)
- recent ejaculation in the days before the test
- vigorous cycling or pressure on the area
- a recent catheter, prostate exam, or urinary procedure
- simply older age, as PSA tends to drift up over time
Because of this, a single elevated PSA is usually a prompt for discussion and often a repeat test, not a diagnosis. Clinicians look at the wider picture, including trends over time, how quickly the value is changing, and prostate size, and they decide whether any further evaluation is worthwhile. Any raised result is best reviewed with a clinician.
What a low Psa can mean
A low PSA result is generally reassuring in the context of prostate screening, and on its own it is usually not a cause for concern. As with any single value, it is still interpreted in context rather than read in isolation.
One useful thing to know is that certain medications can lower PSA. Drugs used to treat an enlarged prostate, such as 5-alpha-reductase inhibitors, can reduce the measured level, and clinicians take this into account so that a treatment-lowered value is not misread as more reassuring than it really is. This is one reason it helps for your clinician to know what you are taking.
Overall, PSA is most useful when it is followed over time and read alongside your age, symptoms, and history. A low or normal reading is best understood as part of that ongoing picture, reviewed together with a clinician rather than as a standalone answer.
Track your Psa over time in Quanome — it reads your lab reports (PDF or photo) on your device, charts each marker against its range, and an AI coach explains what your trends mean alongside your Apple Health and DNA.