PSA stands for prostate-specific antigen, a protein produced by the prostate gland. It’s best known as a blood test used to screen for prostate cancer, but PSA itself isn’t harmful. It plays a normal role in the male reproductive system, and every man has some level of it in his bloodstream. The test measures how much of this protein is circulating in your blood, reported in nanograms per milliliter (ng/mL).
What PSA Actually Does in the Body
The prostate is a small gland that sits just below the bladder and produces the fluid portion of semen. PSA’s job is to help liquefy semen after ejaculation so sperm can move freely. Most PSA stays in semen, but a small amount leaks into the bloodstream. That trace amount is what the PSA test picks up.
A higher-than-expected level in the blood suggests something is affecting the prostate, whether that’s cancer, inflammation, infection, or simply age-related growth. The test doesn’t diagnose cancer on its own. It flags the need for further investigation.
Normal PSA Levels by Age
PSA naturally rises as men get older because the prostate tends to grow with age. What counts as “normal” depends on how old you are:
- Ages 40 to 50: 0 to 2.5 ng/mL
- Ages 50 to 60: 2.5 to 3.5 ng/mL
- Ages 60 to 70: 3.5 to 4.5 ng/mL
- Ages 70 to 80: 4.5 to 5.5 ng/mL
A reading above these ranges doesn’t mean you have cancer. It means your doctor will want to figure out why the number is elevated. Roughly three out of four men with a PSA above 4.0 ng/mL do not have prostate cancer when biopsied.
Why PSA Can Be High Without Cancer
Several common, non-cancerous conditions push PSA levels up. Understanding these helps explain why the test is a starting point, not a final answer.
Benign prostatic hyperplasia (BPH) is an enlarged prostate, common in men over 50. A bigger prostate produces more PSA, which can raise blood levels significantly even though no cancer is present. BPH often causes difficulty urinating or a weak stream.
Prostatitis is inflammation of the prostate, sometimes caused by a bacterial infection. The swelling and irritation trigger extra PSA release. Urinary tract infections can have the same effect by irritating tissue near the prostate.
Physical activity matters too. Ejaculation, vigorous exercise (especially cycling, which puts direct pressure on the prostate), and even a digital rectal exam can temporarily spike PSA levels. Doctors typically advise abstaining from ejaculation for at least 24 hours before a blood draw to avoid a misleadingly high result.
Free PSA and PSA Velocity
When a standard PSA result falls in a gray zone, doctors sometimes order additional PSA-based calculations to get a clearer picture before recommending a biopsy.
Free PSA measures the percentage of PSA circulating unbound to other proteins. Cancer cells tend to produce PSA that binds to proteins, so a lower percentage of free PSA raises suspicion. A free PSA above 25% is generally considered normal. When it drops below 18%, and especially below 12%, doctors are more likely to recommend a biopsy.
PSA velocity tracks how quickly your PSA rises over time, typically across multiple blood draws spaced months apart. A rise of more than 0.75 ng/mL per year has historically been the threshold that raises concern, even if each individual reading falls within the normal range. This is why doctors sometimes order repeat tests rather than acting on a single number.
Medications That Affect Your Results
If you take medications for hair loss or an enlarged prostate (drugs like finasteride or dutasteride, which belong to a class called 5-alpha reductase inhibitors), your PSA reading will be artificially low. These medications cut measured PSA levels roughly in half without actually reducing prostate cancer risk. If you’re on one of these drugs, your doctor will typically double the reported number to estimate your true PSA level.
Who Should Get Tested, and When
PSA screening is not universally recommended for all men. The U.S. Preventive Services Task Force advises that men aged 55 to 69 have an individual conversation with their doctor about whether screening makes sense for them, weighing the potential benefits of catching cancer early against the risks of false positives and unnecessary procedures. For men 70 and older, the Task Force recommends against routine PSA screening because the harms of overdiagnosis and overtreatment tend to outweigh the benefits at that age.
Men at higher risk, including Black men and those with a family history of prostate cancer, often begin these conversations earlier, sometimes in their 40s. The decision is personal and depends on your risk factors, your overall health, and how you weigh the tradeoffs.
What Happens After an Elevated Result
A single elevated PSA reading rarely leads straight to a biopsy. The first step is usually a repeat test, sometimes weeks later, to see if the number stays high or was temporarily elevated. If it remains concerning, doctors may order the free PSA ratio, track PSA velocity, or both.
When these results point toward possible cancer, the next step is typically a multiparametric MRI of the prostate. This specialized imaging scan scores suspicious areas on a five-point scale. Scores of 3 or higher generally warrant a biopsy with image-guided targeting, which is more precise than a standard biopsy. Scores of 1 or 2 suggest low suspicion, and doctors may recommend continued monitoring rather than an immediate biopsy.
The entire process, from an initial elevated PSA to a definitive answer, can take weeks to months. That timeline can feel stressful, but each step narrows the possibilities and reduces the chance of unnecessary procedures.