PSA stands for prostate-specific antigen, a protein produced by your prostate gland. In everyday medical practice, PSA refers to a blood test that measures how much of this protein is circulating in your bloodstream. Doctors use it primarily as a screening and monitoring tool for prostate cancer, though elevated levels can signal several other conditions.
What PSA Actually Does in the Body
The prostate gland produces PSA as part of its normal function. The protein’s main job is to liquefy semen after ejaculation, helping sperm move freely. Small amounts of PSA naturally leak from the prostate into the bloodstream, and that’s what the PSA test measures.
Because all prostate tissue produces PSA, anything that affects the prostate can change how much ends up in your blood. A larger prostate makes more PSA. An inflamed or infected prostate leaks more PSA. And prostate cancer cells tend to produce PSA at higher rates than healthy cells. This is what makes PSA useful as a screening tool, but also what makes it imperfect: the test detects prostate activity, not cancer specifically.
What PSA Numbers Mean
PSA is measured in nanograms per milliliter (ng/mL) of blood. A level above 4.0 ng/mL is generally considered abnormal and may prompt further evaluation, including a possible biopsy. But that threshold isn’t absolute. Some doctors use a lower cutoff of 2.5 ng/mL for younger men and a higher cutoff of 5.0 ng/mL for older men, since PSA levels naturally rise with age as the prostate grows.
A single PSA number doesn’t tell the full story. Doctors often track how your PSA changes over time. A level that rises quickly, even if it stays below 4.0, can be more concerning than a stable reading that sits slightly above it. If your PSA is elevated or rising, your doctor may order additional blood tests, imaging like an MRI, or recommend a prostate biopsy to check for cancer directly.
Why PSA Can Be High Without Cancer
An elevated PSA result does not mean you have cancer. Several common, non-cancerous conditions raise PSA levels:
- Enlarged prostate (BPH): As men age, the prostate often grows larger. More tissue means more PSA production, which is the most common reason for mildly elevated readings.
- Prostate inflammation (prostatitis): Inflammation disrupts the cells that produce PSA and makes blood vessels within the prostate more permeable, allowing more PSA to leak into the bloodstream. Research from Johns Hopkins found that the greater the amount of inflammation, the higher the PSA level.
- Urinary tract infections: Infections in or near the prostate can temporarily spike PSA.
- Recent ejaculation or vigorous exercise: Both can cause a temporary PSA increase, which is why doctors ask you to avoid sexual activity and heavy exercise for 48 hours before the test.
How Accurate the Test Really Is
PSA testing is better at ruling out cancer than confirming it. At the standard 4.0 ng/mL cutoff, the test catches about 44% of prostate cancers (its sensitivity) while correctly identifying 92% of men without cancer (its specificity). Lowering the cutoff to 3.0 ng/mL catches more cancers (59%) but also flags more men who turn out to be cancer-free. Raising it to 5.0 catches fewer cancers (33%) but produces fewer false alarms.
This tradeoff is central to the debate around PSA screening. The test misses some cancers entirely, and it flags many men who don’t have cancer, potentially leading to unnecessary biopsies and anxiety. At the same time, it remains one of the best tools available for catching prostate cancer early, when treatment is most effective.
Free PSA and What It Adds
When a standard PSA result falls in a borderline range, your doctor may order a “free PSA” test. PSA travels through the blood in two forms: bound to other proteins, or free-floating. The ratio of free PSA to total PSA helps distinguish cancer from benign conditions.
Men with prostate cancer tend to have a lower percentage of free PSA. Many doctors recommend a biopsy when free PSA is 10% or less of the total, and suggest considering one when it falls between 10% and 25%. A higher free PSA percentage is generally reassuring, suggesting the elevation is more likely caused by an enlarged prostate or inflammation rather than cancer.
Who Should Get Tested
PSA screening recommendations vary by age. The U.S. Preventive Services Task Force currently advises that men between 55 and 69 make an individual decision about screening after discussing the potential benefits and harms with their doctor. There is no blanket recommendation for or against testing in this age group. For men 70 and older, the Task Force recommends against routine PSA screening, since the risks of overdiagnosis and unnecessary treatment tend to outweigh the benefits at that age.
Men at higher risk for prostate cancer, including Black men and those with a family history of the disease, often begin the screening conversation earlier, sometimes in their 40s. The goal is to establish a baseline PSA level that helps your doctor spot meaningful changes over time rather than relying on a single number in isolation.
Preparing for a PSA Test
Because several everyday activities can temporarily raise PSA, preparation matters for an accurate reading. Avoid ejaculation for at least 48 hours before your blood draw. Research shows that ejaculation causes a significant PSA increase, particularly in men over 49, with 97% of men returning to their baseline level within 48 hours. Skip vigorous exercise, especially cycling, for the same 48-hour window. If you’ve recently had a urinary tract infection or prostate procedure, let your doctor know, as these can elevate PSA for weeks.
The test itself is a simple blood draw, typically from a vein in your arm. Results usually come back within a few days. If your PSA is elevated, it’s the starting point of a conversation, not a diagnosis. Most men with a high PSA do not have prostate cancer, and further testing can clarify what’s actually going on.