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Bloodwork Glossary

Plain-English definitions of commonly-searched bloodwork markers. Each entry has a reference range, what high and low values mean, when to test, and cross-links to related tests. Educational only, not medical advice.

Last updated: 2026-04-21 · Maintained by the VitaLog team

Hormones

SHBG

Sex Hormone-Binding Globulin. Binds testosterone and estradiol in circulation. Determines how much testosterone is free vs bound.

Total Testosterone

All testosterone in circulation, free, albumin-bound, SHBG-bound. The headline number on any TRT panel.

Free Testosterone

Unbound testosterone that can enter tissues and bind androgen receptors. The bioactive fraction.

Estradiol (E2)

Primary estrogen; rises with testosterone aromatization. Too low = joint aches, low libido. Too high = water retention.

Prolactin

Pituitary hormone. Elevation can suppress the HPG axis. Rules out prolactinoma before starting TRT.

TSH

Thyroid-Stimulating Hormone. First-line thyroid screen. Low-T symptoms can be masked thyroid dysfunction.

CBC & hematology

Hematocrit (HCT)

Percentage of blood volume that is red blood cells. TRT raises HCT; safety threshold 54%.

Hemoglobin (HGB)

Oxygen-carrying protein in red blood cells. Correlates with HCT.

Liver enzymes

AST

Aspartate aminotransferase. Found in liver AND muscle, context matters. Heavy training can raise it.

ALT

Alanine aminotransferase. More liver-specific than AST. AST/ALT ratio >1 suggests muscle source when elevated.

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