Testosterone, Free (Calculated)

Fasting Required
CPT: 84402
Hormones

What This Test Measures

Calculated free testosterone based on total T and SHBG using Vermeulen formula; estimates bioavailable T.

Preparation

Fasting required (8-12 hours)
Draw in the early morning (7–10 AM) when testosterone is at its daily peak. If on testosterone BHRT injections, draw at trough — just before your next scheduled injection — for the most clinically meaningful result. Quest may report inflated values for women on BHRT; CPL or LabCorp recommended for trending.
💬 Patient Community Notes

TRT TIMING: Draw at trough — just before your next injection. Calculated free testosterone (from total T, SHBG, and albumin) is considered more reliable than the direct free T assay. For women on BHRT, community guidance indicates LabCorp delivers the most accurate results, as immunoassay methods used by some labs can report falsely elevated values. These notes reflect common practices in TRT/BHRT communities.

Reflects common practices in thyroid, BHRT, and functional medicine communities. This may differ from standard clinical guidelines. Not medical advice — always discuss with your provider.

General guidelines only. Requirements vary by lab and individual. Confirm with your provider before adjusting any medications.

Turnaround Time

Varies by lab

Clinical Notes

Calculated, not directly measured; less accurate than equilibrium dialysis

ICD-10 Codes

Common diagnosis codes associated with this test. Codes are assigned by your provider.

E28.39Other ovarian dysfunction
E29.1Testicular hypofunction
N91.2Amenorrhea, unspecified
R68.89Other specified general symptoms and signs

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Quest Diagnostics--
LabCorp--
Ulta Lab Tests--
Walk-In Lab--
Any Lab Test Now--
Request A Test--
HealthLabs.com--
Private MD Labs--
DirectLabs--
Personalabs--
Life Extension--

Lab Codes

Proprietary codes used by each lab for this test.

Quest Diagnostics
18944(order)
Quest Diagnostics
36170(order_code)

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For informational purposes only

This page is for educational and research purposes only and does not constitute medical advice, diagnosis, or treatment recommendations. ICD-10 and CPT codes are assigned by your healthcare provider. Always consult a qualified healthcare provider before ordering any lab test or making decisions about your health.