Skip to content
DE

Low free testosterone despite normal total testosterone

Clinical review pending

Why free testosterone can be low despite a normal total result, how SHBG affects the picture, and why repeat testing and the measurement method matter.

A hand holds an open blank book with three colored windows.

What this pattern means

Free testosterone can be low even when total testosterone is within the reference range. Sex hormone-binding globulin, or SHBG, is often elevated. This protein binds testosterone, leaving less unbound hormone available to tissues. Men with this pattern often have higher SHBG levels. A normal total result therefore does not rule out low free testosterone. Source 1 Source 2 Source 3 Source 4 Source 5

The reverse pattern, low total testosterone with normal free testosterone, is more common in men with obesity and lower SHBG. Understanding either result starts with knowing which fraction of testosterone each test measures. Source 1

Total, free, and bioavailable testosterone

Total testosterone includes all testosterone in the blood. Free testosterone is the unbound fraction, around 2%, that can enter cells. Laboratories distinguish three measures. Source 1

Measure Fraction included Meaning
Total testosterone Testosterone bound to SHBG and albumin, plus unbound testosterone The usual first measurement when investigating testosterone levels
Free testosterone Testosterone not bound to a protein The unbound fraction; interpretation depends on the measurement method
Bioavailable testosterone Free and albumin-bound testosterone, excluding the SHBG-bound fraction The conventional term for free testosterone plus the fraction loosely bound to albumin

Source 1 Source 2 Source 3 Source 4

Most testosterone circulates bound to proteins: tightly to SHBG or loosely to albumin. These proteins influence the relationship between free and total testosterone. Higher SHBG can reduce the free fraction, but the actual free concentration also depends on total testosterone and hormonal regulation. Source 1

How high SHBG can affect free testosterone

Elevated SHBG can help explain low free testosterone when the total value is normal or even high. It does not inevitably produce a low free result. Several factors can raise SHBG in men. Source 1

  • Older age: SHBG rises with age, so free testosterone tends to decline faster than total testosterone. Source 1

  • Certain antiseizure medications: long-term use has been associated with higher SHBG and lower free testosterone. Source 1

  • Advanced liver disease, or cirrhosis: SHBG can rise while free testosterone falls. Source 1 Source 2

  • HIV: in the cited study, approximately one-third of men with HIV and untreated testosterone deficiency had this pattern. Source 1

An overactive thyroid can also raise SHBG. In the cited small study of nine men and eleven women, average free testosterone in men did not differ significantly between hyperthyroidism and restored normal thyroid function. This does not rule out the thyroid as a relevant part of an individual’s assessment. Source 1

Symptoms associated with low free testosterone and normal total testosterone

In a study of 3,334 men ages 40 to 79, normal total testosterone with low calculated free testosterone was associated with more sexual symptoms and poorer physical function, even after accounting for age. Hemoglobin and bone measures were also less favorable. These are associations, not proof that the free testosterone result caused the symptoms or that treatment would resolve them. Source 1 Source 2

In another study of 231 men with total testosterone near the lower limit, symptoms were similar whether free testosterone was low or normal. Symptoms alone cannot determine whether free testosterone is low. The laboratory finding therefore needs confirmation. Source 1

How a low free testosterone result is confirmed

Confirmation involves a fasting morning blood sample and repeat testing. Free testosterone is either calculated or measured with the reference method, equilibrium dialysis. Source 1

  • Morning testing: total testosterone is measured between 7 and 11 a.m., with separate consideration for shift workers. Source 1

  • Repeat testing: an abnormal finding is checked on another morning under comparable conditions. The cited practical review suggests at least two to three weeks between measurements; that interval does not itself establish a deficiency requiring treatment. Symptoms, the testing method, and potentially temporary influences also need consideration. Source 1

  • Free testosterone: an appropriate calculation using total testosterone, SHBG, and albumin can be useful. Accuracy depends on the underlying measurements and formula; calculated values are not interchangeable with every dialysis method. Direct analog immunoassays are unreliable for measuring free testosterone. Source 1 Source 2

  • LH testing: luteinizing hormone, sometimes assessed alongside FSH, helps distinguish a testicular cause from a hypothalamic or pituitary cause after deficiency has been confirmed. Source 1 Source 2

The reference range for free testosterone also depends on the method used.

Free testosterone reference ranges

A study of 145 healthy, nonobese adult men established a reference interval of 66 to 309 pg/mL, or picograms per milliliter, using standardized equilibrium dialysis. This is specific to the study and method, not a universal cutoff. Total testosterone is expressed here in ng/dL, or nanograms per deciliter. Source 1

Measure Group Reference interval
Total testosterone Healthy, nonobese men ages 19 to 39 264 to 916 ng/dL
Free testosterone Healthy, nonobese men ages 19 to 39 120 to 368 pg/mL
Free testosterone Healthy, nonobese men age 19 and older 66 to 309 pg/mL

Source 1 Source 2

A reference interval describes the distribution in a selected comparison group. It neither guarantees freedom from disease nor defines a narrower “optimal” target for energy, performance, or long-term health. The dialysis intervals above need further validation against health outcomes. In the study, free testosterone declined with age and BMI; the laboratory, method, and population therefore matter when interpreting results. A borderline value alongside relevant symptoms can be a reason to repeat testing. Source 1

What to do after a low result

Low free testosterone with normal total testosterone should be confirmed and discussed with a clinician. A diagnosis of testosterone deficiency requires relevant symptoms together with consistently low results. Benefits and risks are weighed before treatment. Source 1

When SHBG is elevated, the assessment may include medications, liver health, and, depending on the findings, thyroid function. Repeated total testosterone and SHBG measurements, together with an appropriate free testosterone assessment, help show whether the pattern persists.

References

  • Antonio L, Wu FC, O’Neill TW, et al. Low free testosterone is associated with hypogonadal signs and symptoms in men with normal total testosterone. J Clin Endocrinol Metab. 2016;101(7):2647-2657. https://doi.org/10.1210/jc.2015-4106 Source

  • Bikle DD. The free hormone hypothesis: when, why, and how to measure the free hormone levels to assess vitamin D, thyroid, sex hormone, and cortisol status. JBMR Plus. 2020;5(1):e10418. https://doi.org/10.1002/jbm4.10418 Source

  • MedlinePlus. Testosterone levels test. National Library of Medicine. Updated June 5, 2025. Accessed October 17, 2026. Source

  • Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999;84(10):3666-3672. https://doi.org/10.1210/jcem.84.10.6079 Source

  • Narinx N, David K, Walravens J, et al. Role of sex hormone-binding globulin in the free hormone hypothesis and the relevance of free testosterone in androgen physiology. Cell Mol Life Sci. 2022;79(11):543. https://doi.org/10.1007/s00018-022-04562-1 Source

  • Vermeulen A, Kaufman JM, Giagulli VA. Influence of some biological indexes on sex hormone-binding globulin and androgen levels in aging or obese males. J Clin Endocrinol Metab. 1996;81(5):1821-1826. https://doi.org/10.1210/jcem.81.5.8626841 Source

  • Toone BK, Wheeler M, Nanjee M, Fenwick P, Grant R. Sex hormones, sexual activity and plasma anticonvulsant levels in male epileptics. J Neurol Neurosurg Psychiatry. 1983;46(9):824-826. https://doi.org/10.1136/jnnp.46.9.824 Source

  • Maruyama Y, Adachi Y, Aoki N, Suzuki Y, Shinohara H, Yamamoto T. Mechanism of feminization in male patients with non-alcoholic liver cirrhosis: role of sex hormone-binding globulin. Gastroenterol Jpn. 1991;26(4):435-439. https://doi.org/10.1007/BF02782811 Source

  • Monroe AK, Dobs AS, Palella FJ, Kingsley LA, Witt MD, Brown TT. Morning free and total testosterone in HIV-infected men: implications for the assessment of hypogonadism. AIDS Res Ther. 2014;11(1):6. https://doi.org/10.1186/1742-6405-11-6 Source

  • Ford HC, Cooke RR, Keightley EA, Feek CM. Serum levels of free and bound testosterone in hyperthyroidism. Clin Endocrinol (Oxf). 1992;36(2):187-192. https://doi.org/10.1111/j.1365-2265.1992.tb00956.x Source

  • Ramasamy R, Golan R, Wilken N, Scovell JM, Lipshultz LI. Association of free testosterone with hypogonadal symptoms in men with near-normal total testosterone levels. Urology. 2015;86(2):287-290. https://doi.org/10.1016/j.urology.2015.05.007 Source

  • Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. https://doi.org/10.1210/jc.2018-00229 Source

  • Shumaker AD, Leelani N, Roth B, et al. Does my patient have testosterone deficiency? Cleve Clin J Med. 2024;91(2):93-95. https://doi.org/10.3949/ccjm.91a.23064 Source

  • Fritz KS, McKean AJ, Nelson JC, Wilcox RB. Analog-based free testosterone test results linked to total testosterone concentrations, not free testosterone concentrations. Clin Chem. 2008;54(3):512-516. https://doi.org/10.1373/clinchem.2007.094870 Source

  • Jasuja R, Pencina KM, Spencer DJ, et al. Reference intervals for free testosterone in adult men measured using a standardized equilibrium dialysis procedure. Andrology. 2023;11(1):125-133. https://doi.org/10.1111/andr.13310 Source

  • Travison TG, Vesper HW, Orwoll E, et al. Harmonized reference ranges for circulating testosterone levels in men of four cohort studies in the United States and Europe. J Clin Endocrinol Metab. 2017;102(4):1161-1173. https://doi.org/10.1210/jc.2016-2935 Source