The volume measurement, or hct blood test, is the proportion of blood that the red blood cells take up. Hemoglobin, on the other hand, is a density or concentration measurement and is expressed in grams per liter or deciliter. (Hemoglobin is, if you will recall from your high school biology, the iron-based protein that transports oxygen.) RBC is a simple count and is usually expressed as the number of million red blood cells that you have per microliter. Usually, hematocrit is three times the amount of hemoglobin.

Testosterone replacement therapy (TRT) increases hematocrit in most men.  Read more about how to decrease hematocrit.

NOTE: Hematocrit is also part of the CBC panel, so there is no need to order separately if your order already includes CBC.

Approximately 95% of IGF-1 and IGF-II are bound to IGFBP-3, which makes this protein the major carrier of the insulin-like growth factors in circulation. The function of the binding protein is to extend the half-life of the growth factors in the circulation.

Prostate Specific Antigen (PSA) is produced exclusively by cells of the prostate gland. Used in conjunction with the digital rectal examination, PSA is a useful screening test for benign prostate enlargement, prostatitis and prostate cancer development.

The reverse T3 test has to be done at the same time you do the free T3, and you then measure the ratio between the two by dividing the RT3 into the Free T3. The body produces the benign RT3 naturally to rid itself of excess of T4, but in some cases, such as high or low cortisol, RT3 is produced in excess, which can clog cell receptors from receiving T3. FT3 is usually twenty or more times higher than RT3. NOTE: Reverse T3 is analyzed using a specific technique called liquid chromatography/tandem mass spectrometry (LC/MS-MS). There's a special place in the U.S. where these precise machines needed for LC/MS panels run only on two specific days a week. So, sometimes the clock ticks a bit while we wait for samples to return from their initial collection points. Results may take 7 business days.

Estrone (E1) is one of the three estrogens, which also include estriol and estradiol. Estrone is the least abundant of the three and is considered a pro-hormone of estradiol.

This test for adrenal insufficiency includes 4 measurements of your salivary Cortisol level during one day. Cortisol, also known as the "stress hormone" can be either too high or too low which may be a sign of adrenal distress.

This is the lowest QuantiFERON Gold test price in the United States. It is also the most accurate TB test you can buy online without a doctor's visit. The price includes the doctor's order. No hidden fees or surprise bills.

This is the gold standard for the IGRA TB test. The 1 Tube QuantiFERON®-TB Gold Plus is an indirect test for M. tuberculosis infection TB (including disease) and is intended for use in conjunction with risk assessment, radiography, and other medical and diagnostic evaluations. This test does not differentiate between latent and active TB. All institutions, the US government, employers, and agencies accept this test.

The determination of TPO antibody levels is the most sensitive test for detecting autoimmune thyroid disease (eg, Hashimoto's thyroiditis, idiopathic myxedema, and Graves disease) and detectable concentrations of anti-TPO antibodies are observed in most patients with these disorders. The highest TPO antibody levels are observed in patients suffering from Hashimoto thyroiditis. In this disease, the prevalence of TPO antibodies is about 90% of cases, confirming the autoimmune origin of the disease. These autoantibodies also frequently occur (60%–80%) in the course of Graves disease.