How to Interpret Testosterone Lab Results: Free, Total, SHBG, and Bioavailable Explained

A comprehensive testosterone lab panel typically measures four main values: Total Testosterone, Sex Hormone Binding Globulin (SHBG), Free Testosterone (either measured directly or calculated), and sometimes Bioavailable Testosterone. Each number measures a different aspect of testosterone in the blood and each tells you something slightly different about the hormonal picture. Total Testosterone measures ALL the testosterone in your blood — every molecule, whether bound to transport proteins or floating free. It is the most commonly reported value and the simplest to measure. Reference ranges vary by lab but typically: 300-1,000 ng/dL for adult men and 8-60 ng/dL for women. The normal range is wide because individual variation is large, and the same absolute number can be normal for one person and low for another depending on their receptor sensitivity and symptoms. SHBG (Sex Hormone Binding Globulin) is a protein produced by the liver that binds tightly to testosterone and other sex hormones in the blood. Testosterone bound to SHBG is essentially inactive — it cannot enter cells or bind to androgen receptors until it is released. Reference range: about 10-50 nmol/L for men, higher for women. SHBG levels are affected by many factors: low SHBG is associated with obesity, insulin resistance, and some medications. High SHBG is associated with hyperthyroidism, liver disease, and aging. Free Testosterone is the portion of testosterone NOT bound to any transport protein. It is the active, bioavailable form that can enter cells and bind to receptors. Free testosterone is a very small percentage of total testosterone — typically 1-3%. Reference range varies by measurement method: if calculated from total T and SHBG, typically 50-200 pg/mL for men. Free T is more biologically relevant than total T, especially in people with abnormal SHBG levels. Bioavailable Testosterone includes free testosterone PLUS the testosterone loosely bound to albumin (which can be released to cells easily). This is the testosterone actually available to tissues. Reference range: typically 130-680 ng/dL for men. Bioavailable T is considered the most biologically meaningful measure by some clinicians. Key insight: two people with identical TOTAL testosterone can have very different FREE testosterone if their SHBG levels differ. A person with high SHBG may have 'normal' total T but low free T and symptoms of testosterone deficiency. A person with low SHBG may have 'low' total T but adequate free T and no symptoms. This is why relying on total T alone can mislead. Log your lab results over time in Dosed alongside your protocol — the app tracks the full panel (total T, free T, SHBG, estradiol, etc.) and displays the trends on a single timeline so you can see how your numbers respond to protocol changes. This content is for educational and research purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.

Many TRT clinics and general practitioners focus primarily on total testosterone and use a simple rule: if total T is below about 300 ng/dL (or whatever the lab's lower cutoff is), the person is considered hypogonadal and a candidate for treatment. If total T is above 300, they are considered normal regardless of symptoms. This simple rule catches the obvious cases but misses a lot of nuance. **The SHBG problem**: SHBG binds testosterone tightly. A man with total T of 500 ng/dL (clearly 'normal') but SHBG of 80 nmol/L (very high) may have free testosterone in the low range because so much of his testosterone is locked up in SHBG bonds. This person may have all the symptoms of low testosterone — fatigue, low libido, poor recovery, mood changes — despite a 'normal' total T reading. Only by measuring or calculating free T do you see the problem. Conversely, a man with total T of 280 ng/dL (technically below the lab cutoff) but SHBG of 15 nmol/L (very low) may have adequate free T and feel fine. The low SHBG means more of his testosterone is unbound and biologically active. Treating this person for hypogonadism based on total T alone may not be necessary and may even cause problems. **Who has abnormal SHBG?** Low SHBG is common in: obese men (adipose tissue suppresses SHBG production), men with insulin resistance or type 2 diabetes, men on exogenous testosterone or anabolic steroids, men on certain medications (glucocorticoids), men with hypothyroidism. High SHBG is common in: older men (SHBG rises with age), men on certain medications (anticonvulsants, some antifungals), men with hyperthyroidism, men with liver disease (cirrhosis), men on oral estrogen therapy. Because SHBG is so variable, measuring it alongside total testosterone gives a much clearer picture than total T alone. Any comprehensive TRT evaluation should include SHBG. **Calculating free T from total T and SHBG**: several online calculators (ISSAM calculator, Vermeulen equation) use total T, SHBG, and albumin levels to estimate free T mathematically. The calculated free T is usually close to measured free T and is often more reliable than direct free T measurement using some older lab methods. **The symptom question**: ultimately, TRT decisions should be based on BOTH lab values AND symptoms. A man with unambiguously low total T, low free T, AND symptoms (fatigue, low libido, mood issues, muscle loss) is clearly a candidate. A man with borderline low T but NO symptoms may not benefit from treatment. A man with 'normal' T but clear symptoms should have free T and SHBG checked to see if the full picture is really normal. Dosed lets you log symptoms alongside lab values so you can see whether subjective changes correlate with numerical changes over time — the data patterns are more informative than any single lab snapshot.

Testosterone levels vary significantly with age, lifestyle, and individual factors. 'Normal' is a wide range and what is healthy for a 25-year-old athlete is different from what is healthy for a 65-year-old man. **Age-related testosterone levels** (approximate ranges from published research): - **Ages 20-30**: Total T typically 500-1,000 ng/dL. Free T typically 9-30 ng/dL (or ~12-40 pg/mL depending on units). SHBG typically 15-45 nmol/L. - **Ages 30-40**: Total T typically 450-900 ng/dL. Free T typically 8-25 ng/dL. SHBG typically 15-50 nmol/L. - **Ages 40-50**: Total T typically 400-800 ng/dL. Free T typically 6-20 ng/dL. SHBG typically 18-55 nmol/L. - **Ages 50-60**: Total T typically 350-700 ng/dL. Free T typically 5-18 ng/dL. SHBG typically 20-60 nmol/L. - **Ages 60+**: Total T typically 300-650 ng/dL. Free T typically 4-15 ng/dL. SHBG typically 25-70 nmol/L. These are approximate ranges and individual labs report different reference ranges based on their populations. The important trend: total testosterone declines gradually with age (about 1-2% per year after age 30), while SHBG generally rises with age. Both contribute to lower free testosterone as men get older. **Optimal vs normal vs low**: there is a difference between being within the normal range (below the upper cutoff, above the lower cutoff) and being optimized. Many TRT clinics target the UPPER half of the normal range (e.g., 700-1,000 ng/dL for adult men) rather than just keeping patients above the lower cutoff. The reasoning: being at 350 ng/dL is technically 'normal' but many men report feeling significantly better at 700-900 ng/dL. Whether this is medically appropriate is debated — some physicians argue keeping men in the lower-normal range is sufficient and reduces long-term risks, while others argue that upper-normal range matches what young men had and is the right target. **What affects testosterone levels naturally** (besides age): - Sleep: 7-9 hours per night. Sleep deprivation (less than 5 hours) can lower testosterone by 10-15% within a week. - Exercise: resistance training boosts testosterone acutely and chronically. Overtraining (chronic cortisol elevation) can lower testosterone. - Body fat: obesity lowers testosterone (through aromatization of T to estrogen in adipose tissue and through SHBG suppression). - Diet: severe caloric restriction lowers testosterone; adequate calories, protein, and dietary fat support normal levels. - Stress: chronic stress raises cortisol, which suppresses testosterone. - Alcohol: chronic heavy drinking lowers testosterone (acute alcohol use has minimal effect). - Zinc and vitamin D: deficiencies can lower testosterone; supplementation only helps if deficient. - Medications: many prescription medications affect testosterone. Opioids, glucocorticoids, some antidepressants, and ketoconazole can all suppress testosterone significantly. A man with 'low' testosterone levels should investigate these factors before jumping to exogenous treatment. Fixing sleep, losing body fat, treating depression, and adjusting medications can often restore testosterone to normal without TRT. Dosed lets you log not just lab values but also lifestyle factors (sleep, exercise, diet, supplements) so you can identify which changes correlate with testosterone trends over time.

A single testosterone lab result is a snapshot in time — it tells you where you are at one moment but not how you got there or where you are going. To make meaningful decisions about testosterone health and protocol response, you need to track the full panel over time and watch the trends. **What to track on each lab draw**: - Total testosterone - Free testosterone (measured or calculated) - SHBG - Albumin (needed for accurate free T calculation) - Estradiol (testosterone converts to estradiol; TRT users need to monitor estrogen levels) - Hematocrit (TRT can raise red blood cell count; this must be monitored) - PSA (for men over 40 on TRT; monitors prostate health) - Lipid panel (testosterone affects cholesterol in some individuals) - Complete blood count (full CBC provides context) - Comprehensive metabolic panel (liver, kidney, glucose) That is a comprehensive panel. Some clinicians also recommend: DHEA-S, cortisol (AM and PM), thyroid panel (TSH, free T3, free T4), and inflammatory markers (CRP, homocysteine). **Frequency of labs**: - **Pre-treatment baseline**: draw labs before starting any protocol. Ideally two baseline draws on different days to account for normal fluctuation. - **After protocol changes**: 6-8 weeks after starting TRT or changing dose. Testosterone levels take 4-6 weeks to stabilize after a dose change. - **Routine monitoring**: every 3-6 months for the first year on TRT, then every 6-12 months if stable. - **Additional draws**: after any significant life change (major weight loss, sleep change, medication addition, new symptoms). **Timing of the draw**: testosterone has a daily rhythm — levels peak in the morning (around 8 AM) and decline through the day. For consistent tracking, always draw blood at the same time of day (ideally early morning, 8-10 AM). Comparing a 7 AM draw to a 2 PM draw is comparing apples to oranges. For men on injectable TRT, the timing within the injection cycle also matters. If you inject weekly on Sunday, your peak is around Tuesday-Wednesday and your trough is Saturday-Sunday. The standard practice is to draw labs at the TROUGH (just before your next injection) because that tells you the lowest point of your cycle. If you draw at the peak, the number looks higher but does not reflect the full picture. **What to look for in trends**: 1. **Are the numbers stable?** If total T is 700 ng/dL at every draw for a year, the protocol is working consistently. 2. **Are you trending in the right direction?** If total T was 350 before TRT and is now 650 after 6 months, the trend is clearly positive and the protocol is working. 3. **Are side effect markers stable?** Hematocrit rising above 52-54% is concerning and may require dose reduction or therapeutic phlebotomy. Estradiol rising too high causes mood and body composition issues. 4. **Do the trends match symptoms?** If your numbers are rising but you feel worse, something else is happening. If your numbers are stable but you feel better, maybe the protocol is working through some non-hormonal mechanism (placebo effect, improved sleep, better diet). **The value of longitudinal data**: a single lab result can be misleading. A year of lab data showing consistent trends tells the real story. Most TRT clinics do not maintain good longitudinal records for their patients — they focus on the current visit. Patients who maintain their own records (in Dosed or a similar tracker) often have better data than their clinicians because they can see patterns across years. Dosed is built specifically for this longitudinal tracking. Log each lab draw with the date, time, and all the values. The app displays trends over time alongside your protocol changes, injection dates, and subjective symptoms — so you can see exactly how your body responds to each change. Bring the data to your medical appointments to have informed conversations with your provider.