Progesterone, Free, With Total Progesterone, LC/MS-MS

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Turnaround Time: 8 - 12 days
CPT Code:

84144; 84999

Test Type: 1.6 mL Serum (preferred) or plasma
Stability Time:



Room temperature

6 days


6 days


6 days

Freeze/thaw cycles

Stable x6


Progesterone plays an important role in the secretory transformation of the endometrium, maintenance of gestation, and relaxation of the myometrium. Progesterone is also a marker for ovulation and luteal phase of the menstrual cycle. Steroid hormones (like progesterone) circulate in the blood in protein-bound and free forms, and it is the free form that exhibits biological activity. The free form of progesterone is expected to reflect the biological activity of progesterone.

The test is not accurate for hemolyzed samples. Cortisol and other hormones that bind transcortin (corticosteroid-binding globulin) may affect the percentage of free progesterone.

Results of this test are for investigational purposes only. The performance characteristics of this assay have been determined by LabCorp. The result should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.

Batra S, Bengtsson IP, Grundsell H, Sjöberg NO. Levels of free and protein-bound progesterone in plasma during late pregnancy. J Clin Endocrinol Metab. 1976 Jun; 42(6):1041-1047. PubMed 932171

Shintani K, Yoshida N, Sekiba K. Changes in free progesterone in the serum, peritoneal fluid and follicular fluid through the menstrual cycle and pregnancy. Endocrinol Jpn. 1987 Apr; 34(2):221-230. PubMed 3622390

Collection Details:

Collection Instructions:

Red-top tube, gel-barrier tube, lavender-top (EDTA) tube, or green-top (sodium heparin) tube.

To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Freeze (preferred) or refrigerate.