How do I check my testosterone levels?

How to Check Testosterone Levels

Measure total testosterone on two separate mornings (between 8-10 AM) while fasting, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a laboratory certified by the CDC's Hormone Standardization Program. 1, 2, 3

Primary Testing Protocol

Timing and Sample Collection

• Draw blood in the early morning (8-10 AM) to capture peak testosterone levels due to diurnal variation 1, 2
• Ensure the patient is fasting before the blood draw, as both glucose loads and mixed meals can transiently lower testosterone by 100-123 ng/dL within 60 minutes 4
• Repeat the measurement on a second separate morning to confirm results, as day-to-day testosterone variability is significant 1, 2

Laboratory Method Requirements

• Use liquid chromatography-tandem mass spectrometry (LC-MS/MS) rather than immunoassays, as this provides superior accuracy 3, 5
• Select a laboratory certified by the CDC's Hormone Standardization (HoST) Program to ensure accuracy-based measurement 3, 5
• Use the same laboratory and methodology for both measurements to minimize analytical variability 1

Diagnostic Threshold

• Low testosterone is defined as <300 ng/dL on both measurements 1, 2, 6
• Approximately 11% of men may transiently drop below 300 ng/dL after glucose intake and 56% after a mixed meal, which is why fasting samples are critical 4

When to Add Free Testosterone Testing

Order free testosterone only in specific circumstances where sex hormone-binding globulin (SHBG) levels may be altered: 1, 6

• Obesity (low SHBG can falsely lower total testosterone while free testosterone remains normal) 1, 6
• Total testosterone levels that are borderline (slightly above or below 300 ng/dL) 5
• Use equilibrium dialysis method for free testosterone measurement—this is the gold standard and far more accurate than analog immunoassays or calculated methods 1, 6, 3

Follow-Up Testing When Testosterone is Low

Once you confirm low testosterone (<300 ng/dL on two occasions), proceed with: 1, 2, 6

• Serum luteinizing hormone (LH) to distinguish primary hypogonadism (high LH = testicular failure) from secondary hypogonadism (low/normal LH = pituitary/hypothalamic dysfunction) 1, 2, 6
• Serum prolactin if LH is low or low-normal, as hyperprolactinemia can suppress testosterone production 1, 2, 6
• Consider endocrinology referral if prolactin is persistently elevated without clear cause 1

High-Risk Populations Requiring Testing

Test testosterone even without classic symptoms in patients with: 1, 6

• Unexplained anemia 1, 2, 6
• Bone density loss or osteoporosis 2, 6
• Type 2 diabetes 2, 6
• HIV/AIDS 2, 6
• History of chemotherapy or testicular radiation 1, 6
• Chronic opioid use 1, 6
• Male infertility 1, 6
• Pituitary dysfunction 1, 6
• Chronic corticosteroid use 1, 6

Critical Pitfalls to Avoid

• Never diagnose testosterone deficiency on a single measurement—intra-individual variability is too high 1, 2
• Never rely on screening questionnaires (like ADAM or AMS) as substitutes for laboratory testing due to poor sensitivity and specificity 1, 6
• Avoid analog free testosterone immunoassays—they have limited reliability compared to equilibrium dialysis 1, 6
• Do not test in the afternoon or evening—testosterone levels decline throughout the day and may be 20-30% lower by afternoon 1, 7
• Never diagnose based solely on lab values—diagnosis requires both low testosterone levels AND corresponding clinical symptoms (reduced energy, sexual dysfunction, decreased muscle mass, etc.) 2, 8
• Do not test non-fasting samples—meals can cause significant transient drops in testosterone that resolve within 2-3 hours 4