Prostate-specific antigen (PSA) is a protein produced by cells of the prostate gland. Small amounts circulate in the blood of all men, but elevated levels can signal prostate cancer, benign prostatic hyperplasia (BPH), or prostate inflammation (prostatitis).

Why PSA matters

Prostate cancer is the second most common cancer in men worldwide. When caught early, 5-year survival exceeds 99%. PSA testing is the primary blood-based screening tool and can identify tumors before they produce symptoms.

However, PSA is prostate-specific, not cancer-specific. An elevated PSA can reflect cancer, but it can also reflect BPH, prostatitis, recent ejaculation, urinary tract infection, a recent digital rectal exam, or vigorous bicycling. This is why PSA should always be interpreted in context.

Reference ranges

General adult male thresholds:

• Under 4.0 ng/mL: traditional normal cutoff

• 4.0–10.0 ng/mL: "gray zone" — roughly 25% cancer risk

• Above 10.0 ng/mL: greater than 50% cancer risk

Age-adjusted ranges refine interpretation:

• 40–49 years: under 2.5 ng/mL

• 50–59 years: under 3.5 ng/mL

• 60–69 years: under 4.5 ng/mL

• 70+ years: under 6.5 ng/mL

Beyond the single number

PSA density (PSA divided by prostate volume) and PSA velocity (rate of change over time) add clinical precision. A PSA that doubles in under a year is more concerning than a stable elevated value. A free PSA percentage below 25% raises cancer likelihood.

When to screen

USPSTF guidance supports shared decision-making for men 55–69, with individual risk factors — family history, African American ancestry, BRCA mutations — lowering the recommended start age to 40–45.

What to do with results

An elevated PSA typically prompts:

1. Repeat testing to confirm, avoiding confounders like recent ejaculation or exercise

2. Digital rectal exam and prostate MRI if confirmed

3. Potential biopsy if MRI or velocity suggests cancer

Never interpret a single PSA in isolation — baseline plus trend plus clinical context is the standard.

Lifestyle factors affecting PSA

• Ejaculation within 48 hours can elevate PSA

• Vigorous cycling can temporarily raise PSA

• 5-alpha-reductase inhibitors (finasteride, dutasteride) lower PSA by roughly 50%

• Obesity can falsely lower PSA via hemodilution

• Prostatitis can dramatically elevate PSA; recheck after treatment