Before You Start Testosterone, Check These Five Things
A low number on a single afternoon draw is not a diagnosis. Here's the workup I insist on before anyone starts TRT with me — and what fixing the upstream problem often does on its own.
- 01Diagnosis requires two morning total testosterone levels drawn before 10 a.m., not one convenience draw.
- 02Total testosterone can mislead. SHBG and free testosterone change the interpretation, especially with obesity or insulin resistance.
- 03LH and FSH tell you whether the problem is the testicle or the signal above it — and occasionally reveal a pituitary issue.
- 04Untreated sleep apnea, iron deficiency, thyroid disease, and depression all reproduce the symptom list.
- 05If fertility matters now or later, that decision has to happen before the first dose, not after.
Men come in with the symptom list already assembled: flat motivation, worse workouts, irritability, low libido, brain fog. Sometimes that is testosterone. Often it is something else that happens to produce the same list — and one afternoon lab draw isn't enough to tell the difference.
Here's what I check first.
1. Two morning levels, drawn properly
Testosterone follows a daily rhythm and peaks in the early morning. A 4 p.m. draw can read 200 points lower than the same man's 8 a.m. value. Guidelines call for two separate fasting morning measurements before 10 a.m., on different days, ideally not during acute illness.
I have seen a great many men labeled hypogonadal on a single afternoon result who were entirely normal on a proper draw.
2. SHBG and free testosterone
Total testosterone measures bound and unbound hormone together. Sex hormone-binding globulin determines how much is actually available. Obesity, insulin resistance, and hypothyroidism lower SHBG; aging, alcohol, and liver disease raise it. A man with low SHBG can have a low total and a perfectly adequate free level — and treating him is treating a number, not a patient.
3. LH and FSH
These separate primary testicular failure (high LH, low testosterone) from a signaling problem higher up (low or inappropriately normal LH). The second pattern deserves a prolactin level, and sometimes imaging. It's uncommon, but it's the finding you don't want to miss by starting therapy and never asking.
4. The conditions that mimic it
Before I attribute fatigue and low drive to hormones, I want to have ruled out:
- Obstructive sleep apnea — extremely common in this population and a direct suppressor of testosterone.
- Iron deficiency, with ferritin, not just hemoglobin.
- Thyroid disease.
- Depression, which shares nearly the entire symptom list.
- Medications: opioids, high-dose steroids, and some antidepressants.
Treating sleep apnea alone raises testosterone in a meaningful subset of men.
5. Fertility, decided in advance
Exogenous testosterone suppresses the signal that drives sperm production. For some men this is reversible after stopping; for some it isn't, and recovery can take a year or more. If children are a possibility — now or in five years — we talk about it before the first dose and consider alternatives that preserve the axis.
And the boring baseline
Hematocrit, PSA where age-appropriate, blood pressure, and lipids before starting; hematocrit and testosterone rechecked at three months. Erythrocytosis is the side effect I manage most often, and it is manageable when you're actually looking for it.
What this is not
This is not gatekeeping. Testosterone deficiency is real, underdiagnosed in plenty of men, and treatment changes lives when the diagnosis is right. The workup exists so that when we do treat, we're treating the thing that's actually wrong.
A note on access: because testosterone is a controlled substance, I can only prescribe it in states where I hold active DEA registration — Indiana, Nevada, New Mexico, Pennsylvania, and Texas.
References
- Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744.
- Mulhall JP, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol. 2018;200(2):423-432.
- Lincoff AM, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). N Engl J Med. 2023;389(2):107-117.
- Wittert G, et al. Testosterone treatment to prevent or revert type 2 diabetes (T4DM). Lancet Diabetes Endocrinol. 2021;9(1):32-45.
- Kim SD, Cho KS. Obstructive Sleep Apnea and Testosterone Deficiency. World J Mens Health. 2019;37(1):12-18.
Related care
If this is what you're working through, read more about Testosterone Replacement Therapy (TRT) for Men.
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