Ordering Recommendation

Provides a calculated value for free testosterone concentration using total testosterone measured by immunoassay. Use to evaluate hypogonadism in cisgender males with a total testosterone concentration at the lower limit of normal. May be used to evaluate testosterone status in individuals with protein-binding abnormalities or to monitor testosterone hormone therapies. Not recommended when low testosterone concentrations, such as those found in children and cisgender females, are expected. For these individuals, testing by mass spectrometry is recommended; refer to Testosterone, Free (Adult Females, Children, or Individuals on Testosterone-Suppressing Hormone Therapy) (0081059).

Mnemonic

FREE T2

Methodology

Quantitative Electrochemiluminescent Immunoassay
Total Testosterone and SHBG are measured and free testosterone is estimated from these measurements.

Performed

Sun-Sat

Reported

Within 24 hours

New York DOH Approval Status

This test is New York DOH approved.

Specimen Required

Patient Preparation

Collect specimen between 6-10 a.m.

Collect

Serum separator tube or green (lithium heparin).

Specimen Preparation

Separate serum from cells ASAP or within 2 hours of collection. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.4 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

EDTA plasma.

Remarks
Stability

After separation from cells: Ambient: 48 hours; Refrigerated: 1 week; Frozen: 2 months

Reference Interval

Male:
14-15 years:  3-138 pg/mL
16-17 years:  38-173 pg/mL
18 years and older: 47-244 pg/mL

Tanner Stage IV:  35-169 pg/mL
Tanner Stage V:  41-239 pg/mL

Interpretive Data

Free testosterone concentration is calculated using total testosterone (measured by immunoassay) and the binding constant of testosterone and sex hormone-binding globulin (SHBG). Testosterone immunoassays are both imprecise and inaccurate at low testosterone concentrations, such as those found in children and cisgender females. For these individuals, testing by mass spectrometry is recommended; refer to Testosterone, Free (Adult Females, Children, or Individuals on Testosterone-Suppressing Hormone Therapy) (ARUP test code 0081059).

For individuals on testosterone hormone therapy, refer to cisgender male reference intervals. No reference intervals have been established for males younger than 14 years or for cisgender females. For a complete set of all established reference intervals, refer to ltd.aruplab.com/Tests/Pub/0070111.

Compliance Category

FDA

Note

Hotline History

N/A

CPT Codes

84402

Components

Component Test Code* Component Chart Name LOINC
0070113 Testosterone, Free Calculation 2991-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.

Aliases

  • Free testosterone
  • serum testosterone free
Testosterone, Free (Adult Males or Individuals on Testosterone Hormone Therapy)