Testing Your Testosterone

So you want to know what your testosterone levels actually are. Good. Knowledge is power. But testing testosterone isn't as simple as just getting "a blood test." There are right ways and wrong ways to do this.

When to Test

Time of Day Matters - A LOT

Always test in the morning, ideally between 7:00 AM and 10:00 AM.

Testosterone peaks in the early morning and can drop 20-40% by afternoon and evening. If you test at 3 PM, you might get a falsely low result and think you have a problem when you don't.

Fasting or Not?

A light fasting state is generally preferred (12+ hours without food), though this is less critical than the timing. Some research suggests eating can slightly lower testosterone readings.

More importantly, fasting is required for other tests you'll likely be getting at the same time (like glucose and lipids).

How Many Tests?

One test is not enough.

Testosterone levels fluctuate day to day. You could test low one morning because you slept poorly, were stressed, or were fighting off an illness. A single low reading shouldn't be the basis for a TRT decision.

Most guidelines recommend at least two separate morning measurements showing low testosterone before considering a diagnosis.

What to Test

Here's a complete panel for evaluating testosterone status:

The Essential Tests

• Total Testosterone - The headline number
• SHBG - To understand how much T is actually available
• LH - Is your brain sending the signal?
• FSH - Related to sperm production; helps diagnose type
• Estradiol (sensitive assay) - The estrogen check

The Supporting Cast

• CBC (Complete Blood Count) - Baseline for hematocrit monitoring
• Comprehensive Metabolic Panel - Liver, kidney function, blood sugar
• Lipid Panel - Cholesterol baseline
• TSH - Thyroid can mimic low-T symptoms
• Prolactin - If low LH, rules out pituitary issue
• Vitamin D - Affects testosterone production
• HbA1c - Diabetes/insulin resistance check

If your SHBG is in the single digits, ask for:

• Fasting insulin (to check for insulin resistance)
• Liver function tests (if not already included)
• Consider glucose tolerance testing

Understanding Your Results

Total Testosterone

Level	Interpretation
<300 ng/dL	Generally considered low
300-400 ng/dL	Low-normal, may cause symptoms in some
400-600 ng/dL	Mid-range normal
600-800 ng/dL	Solid normal
800-1000+ ng/dL	Upper normal

Note: Reference ranges vary by lab. Always look at your specific lab's ranges.

Total testosterone alone is almost meaningless.

Without knowing your SHBG, a total testosterone number tells you very little. Two men with the same total testosterone can have very different free testosterone levels - and feel completely different. For the full explanation of why SHBG matters and how it affects your available testosterone, see Chapter 3: Testosterone in Your Blood.

Free testosterone is what your body actually uses. That's the number to focus on, not total.

Free Testosterone (Calculated)

Level	Interpretation
<10 ng/dL	Low - likely symptomatic
10-15 ng/dL	Low-normal, may cause symptoms
15-25 ng/dL	Good range for most men
25-30 ng/dL	Upper limit
>30 ng/dL	High

Always use calculated free T (from Total T + SHBG), not direct assay.

This is the number that matters. When optimizing TRT, you're targeting a free testosterone level, not a total testosterone level. If your SHBG is high, you may need a higher total testosterone to achieve adequate free testosterone - and that's perfectly fine.

LH and FSH

Pattern	What It Suggests
Low T, High LH, High FSH	Primary hypogonadism (testicular problem)
Low T, Low/Normal LH, Low/Normal FSH	Secondary hypogonadism (brain problem)
Normal T, Normal LH, Normal FSH	Everything's working

SHBG

SHBG Level	Interpretation
<10 nmol/L	Very low - possible metabolic issue
10-30 nmol/L	Low-normal range
30-50 nmol/L	Mid-normal range
>50 nmol/L	High - less free testosterone available

Estradiol

For men, estradiol ranges:

• Below 20 pg/mL - Too low. Causes joint pain, low libido, mood issues, and bone loss
• 20-40 pg/mL - Good range for most men
• 40-50 pg/mL - Upper range, often fine if no symptoms
• Above 50 pg/mL - Can cause symptoms, but not inherently bad if you feel fine

Important: Use the "sensitive" or "LC/MS" estradiol test for men, not the standard test designed for women.

The ratio matters as much as the number. A testosterone:estradiol ratio around 20:1 tends to feel good for most men, even if estradiol is on the higher side. A guy with 1000 ng/dL testosterone and 50 pg/mL estradiol may feel great, while someone with 500 ng/dL and the same estradiol might have symptoms.

If you have no symptoms, don't chase numbers. Some men obsess over getting estradiol into some "optimal" range when they feel perfectly fine. If you're not experiencing water retention, nipple sensitivity, mood issues, or libido problems - leave it alone.

The Free Testosterone Problem (Again)

We covered this in Chapter 3, but it bears repeating:

Do not rely on direct free testosterone tests.

Most labs use an inaccurate "analog" method for direct free T. The results can be wildly off.

Instead: Calculate free testosterone from Total T + SHBG + Albumin using the Vermeulen equation. Many online calculators exist for this.

Testing on TRT

If you're already on TRT, testing is different:

Timing Relative to Injection

The timing of your blood draw relative to your last injection matters enormously:

When to Test	What It Shows
Trough (right before next injection)	Your lowest point - how low you go
Peak (24-48 hours after injection)	Your highest point - checks for excess
Mid-point	A reasonable average of your levels

For most people on TRT, testing at trough (right before your next injection) is most useful. This tells you the minimum level you're maintaining. If your trough is good, you're covered throughout your cycle.

Some doctors prefer testing 48-72 hours after injection. Just be consistent about when you test, so you can compare results over time.

Testing with Different Delivery Methods

Method	When to Test
Weekly injections	Morning of injection day (trough) or 3-4 days after
Twice-weekly injections	Morning before any injection
Daily gel/cream	Before applying (to see baseline), or 2-6 hours after (to see peak)
Pellets	4-6 weeks after insertion for peak, then periodically

What Else Should You Test Initially?

Before starting TRT, your doctor should check:

• PSA (Prostate-Specific Antigen) - Baseline for prostate monitoring
• Hematocrit/Hemoglobin - Baseline before TRT increases it
• Blood pressure - Baseline measurement
• Consider: Bone density scan - If severely low T for extended period
• Consider: Sleep study - If symptoms of sleep apnea

Age and Testosterone: It's Complicated

The relationship between age and testosterone is more nuanced than the "1-2% decline per year" you often hear. For the full picture on how age affects testosterone - and why healthy older men often maintain youthful levels - see Chapter 7: What Affects Testosterone.

Be skeptical of "normal for your age" reasoning.

If a doctor tells you your testosterone is "normal for a 60-year-old," that may just mean it's similar to other unhealthy 60-year-olds in the reference population. It doesn't mean it's optimal or that you should accept feeling terrible.

The real question is: How do you feel, and is low testosterone contributing to symptoms?

Red Flags That Warrant Further Investigation

If your initial tests show any of these, additional workup is needed:

Get further evaluation if:

• LH is elevated but testosterone is low → testicular issue
• LH is very low with low testosterone → pituitary issue (may need MRI)
• Prolactin is elevated → possible pituitary adenoma
• Estradiol is very high → investigate source
• Hematocrit already elevated before TRT → need monitoring/evaluation
• PSA is elevated → prostate evaluation before TRT

Quick Recap

• Test in the morning (7-10 AM) - afternoon tests will be falsely low
• Get at least two tests before any diagnosis
• Essential panel: Total T, SHBG, LH, FSH, sensitive estradiol
• Don't trust direct free T tests - calculate it instead
• On TRT: Test at trough (before injection) for most useful info
• Age is overrated: Healthy older men often maintain good levels; don't accept "normal for your age"
• Symptoms + numbers: Both matter for treatment decisions
• Red flags in results warrant further investigation

---

Next up: Signs of Low Testosterone - What does low testosterone actually feel like? (It's not just about the bedroom.)