Bioavailable Testosterone
Hormones marker
Bioavailable Testosterone
Category: Hormones
Unit: nmol/L
Testosterone that is free or loosely bound to albumin. Represents the portion available to tissues (free T + albumin-bound T).
PED Notes
Bioavailable testosterone includes both free testosterone and albumin-bound testosterone (which can readily dissociate). It excludes only SHBG-bound testosterone. This is a more comprehensive measure of 'usable' testosterone than free T alone. Common on US lab panels (Quest, LabCorp) where it's reported in ng/dL. On AAS/TRT, bioavailable T will be elevated proportionally to total T, modified by SHBG status.
Understanding Bioavailable T:
- Bioavailable T = Free T + Albumin-bound T (approximately 30-50% of total T)
- SHBG-bound T is NOT bioavailable (tightly bound, does not dissociate at tissues)
- More clinically useful than total T when SHBG is abnormal
If low (off-cycle):
- Check total T, free T, and SHBG to understand the cause
- High SHBG will lower bioavailable T even with normal total T
- See Free Testosterone and SHBG management protocols
If elevated (on cycle/TRT):
- Expected -- no intervention needed unless experiencing side effects
- Monitor androgenic side effects (acne, hair loss, prostate symptoms)
Supplements & Lifestyle:
- Same protocols as Free Testosterone
- Boron (10mg/day) can lower SHBG and increase bioavailable fraction
References:
- Naghii, M. R., Mofid, M., Asgari, A. R., Hedayati, M., & Daneshpour, M.-S. (2011). Comparative effects of daily and weekly boron supplementation on plasma steroid hormones. Journal of Trace Elements in Medicine and Biology, 25(1), 54-58. DOI: 10.1016/j.jtemb.2010.10.001
- Pilz, S., Frisch, S., Koertke, H., et al. (2011). Effect of vitamin D supplementation on testosterone levels in men. Hormone and Metabolic Research, 43(3), 223-225. DOI: 10.1055/s-0030-1269854
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
3.8 - 20 nmol/L
VitalMetrics Range
7 - 24 nmol/L