Strongyloides serology; suspicion of parasitic infection.

Serology for syphilis; screening and confirmation.

Serology including titer; for syphilis diagnostics.

T3; thyroid function.

Free T4; thyroid function.

TBG; thyroid hormone transport.

THC in blood; recent exposure.

Screening for Toxoplasma gondii; serology.

Toxoplasma IgG and IgM; recent or past infection.

Transferrin; iron transport protein.

Transferrin saturation; iron transport saturation.

Triglycerides; part of lipid profile.

TSH; primary screening of thyroid function.

TSH and free T4; for thyroid function assessment.

TSH plus free T4 and FT3 for assessment of thyroid function.

TRAb; for Graves' disease and thyroid diagnostics.

Urea; protein breakdown and kidney function.

Uric acid; gout and kidney stones.

VZV-IgG; immunity against chickenpox.

VZV-IgA; supplementary serology.

VZV‑IgM; indication of recent infection.

Vitamin A; vision, skin, and immunity.

Active Vitamin B1; energy metabolism and neurological function.

Vitamin B12; for suspected deficiency or absorption issues.