Evidence-Based Supplement & Herb Guides

Oxytocin Blood Test: Hormone Levels, Function, and Results

Learn what an oxytocin blood test can and cannot show, why normal ranges are uncertain, how assays differ, and how oxytocin functions in labor, lactation, and the brain.

An oxytocin blood test measures oxytocin in plasma or serum, but it is not a standard diagnostic test for bonding, autism, anxiety, sexual function,...

Pituitary Hormone Test Panel: ACTH, TSH, LH, FSH, Prolactin, GH, IGF-1, and Results

Understand a pituitary hormone panel including ACTH, TSH, LH, FSH, prolactin, GH, and IGF-1, with result patterns, timing, pitfalls, and follow-up tests.

A pituitary hormone test panel evaluates several hormone systems controlled by the pituitary gland. It commonly includes ACTH with cortisol, TSH with free T4,...

Pituitary Tumor Hormone Panel: Prolactin, ACTH, GH, IGF-1, TSH, LH, FSH, and Results

Learn how a pituitary tumor hormone panel evaluates prolactin, ACTH, cortisol, GH, IGF-1, TSH, LH, and FSH for secreting tumors, deficiencies, and mass effects.

A pituitary tumor hormone panel determines whether a sellar lesion is secreting excess hormone, compressing normal pituitary tissue, or both. The panel commonly measures...

Prolactin Blood Test: High, Low, Normal Range, Pituitary Tumor, and Results

Understand prolactin blood test results, including high and low levels, normal ranges, medicine effects, macroprolactin, prolactinoma, pituitary tumors, and follow-up testing.

A prolactin blood test measures a hormone made mainly by the pituitary gland. Prolactin supports breast development and milk production, but it also affects...

Thyroid-Stimulating Hormone (TSH) Test: Pituitary-Thyroid Axis and Results

Learn how to interpret TSH with free T4 across the pituitary-thyroid axis, including primary thyroid disease, central hypothyroidism, TSHoma, assay interference, and treatment monitoring.

A thyroid-stimulating hormone test measures TSH, the pituitary signal that tells the thyroid gland to make thyroid hormone. It is the most common first...

Adiponectin Blood Test: Low Levels, Insulin Resistance, and Results

Learn what an adiponectin blood test measures, why low levels may accompany insulin resistance, how ranges vary, and what high or abnormal results can mean.

An adiponectin blood test measures a hormone made mainly by fat cells that helps the body respond to insulin, use fatty acids, and regulate...

Amylin Blood Test: Pancreatic Hormone, Glucose Control, and Results

Understand what an amylin blood test measures, how the pancreatic hormone affects glucose and appetite, and what low, high, fasting, or stimulated results may mean.

An amylin blood test measures a pancreatic hormone released from beta cells alongside insulin. Amylin helps limit the rise in blood glucose after eating...

C-Peptide Blood Test: High, Low, Normal Range, Diabetes, and Results

Learn how a C-peptide blood test measures pancreatic insulin production, what high or low results mean, how ranges vary, and how it helps evaluate diabetes and hypoglycemia.

A C-peptide blood test shows how much insulin your pancreas is making. Beta cells release insulin and C-peptide in equal amounts when they split...

Fasting Insulin Test: High Levels, Normal Range, Insulin Resistance, and Metabolic Health

Learn how fasting insulin testing relates to insulin resistance and metabolic health, why ranges vary, and what high or low results mean when compared with glucose.

A fasting insulin test measures the insulin circulating after a period without calories, usually 8 to 12 hours. It can show how hard the...

Gastrin Blood Test: High Levels, Stomach Acid, Zollinger-Ellison Syndrome, and Results

Learn why a gastrin blood test is ordered, how PPIs and stomach acid affect results, and when high levels may suggest Zollinger-Ellison syndrome or low acid.

A gastrin blood test measures a hormone that tells the stomach to produce acid. It is mainly ordered when doctors suspect Zollinger-Ellison syndrome, a...

Ghrelin Blood Test: Hunger Hormone, High and Low Levels, and Results

Learn what a ghrelin blood test measures, why total and active forms differ, and how fasting, weight loss, obesity, surgery, and sample handling affect high or low results.

A ghrelin blood test measures a stomach-derived hormone involved in hunger, meal timing, growth hormone release, glucose regulation, and energy balance. Ghrelin usually rises...

Glucagon Blood Test: High, Low, Normal Range, and Glucose Control

Learn what a glucagon blood test measures, why high or low levels occur, how ranges and assay methods differ, and when results may suggest glucagonoma or impaired glucose counter-regulation.

A glucagon blood test measures a pancreatic hormone that raises blood glucose when it begins to fall. Alpha cells release glucagon during fasting, exercise,...

Glucagon-Like Peptide-1 (GLP-1) Test: Incretin Hormone, Diabetes, and Results

Learn what a GLP-1 test measures, why active and total results differ, how meal testing works, and how to interpret high or low GLP-1 levels in context.

A glucagon-like peptide-1 test measures GLP-1, a short-lived gut hormone released after food reaches the intestine. GLP-1 helps the pancreas release insulin when glucose...

Glucose-Dependent Insulinotropic Peptide (GIP) Test: Incretin Hormone and Results

Learn what a GIP test measures, how active and total GIP differ, why meal timing and sample handling matter, and what high or low results may mean.

A glucose-dependent insulinotropic peptide test measures GIP, an incretin hormone released mainly from K cells in the upper small intestine after eating. GIP helps...

HOMA-IR Test: Insulin Resistance Score, Fasting Insulin, and Results

Calculate and understand HOMA-IR, including fasting requirements, formulas, common cutoffs, causes of high or low scores, limitations, and follow-up testing.

HOMA-IR is a calculated estimate of insulin resistance based on fasting glucose and fasting insulin measured from the same blood draw. A higher score...

Hypoglycemia Hormone Test Panel: Insulin, C-Peptide, Proinsulin, Beta-Hydroxybutyrate, and Results

Understand a hypoglycemia hormone panel, including insulin, C-peptide, proinsulin, beta-hydroxybutyrate, critical-sample timing, result patterns, and next steps.

A hypoglycemia hormone panel is a group of blood tests collected while plasma glucose is genuinely low. The core measurements—glucose, insulin, C-peptide, proinsulin, and...

Insulin Blood Test: High, Low, Normal Range, Insulin Resistance, and Results

Learn how an insulin blood test is used, what fasting ranges mean, why insulin may be high or low, and how results relate to insulin resistance, diabetes, and hypoglycemia.

An insulin blood test measures the amount of insulin in serum or plasma at a specific moment. Insulin is released by pancreatic beta cells...

Insulin Resistance Blood Test Panel: Fasting Insulin, Glucose, C-Peptide, HOMA-IR, and Results

Understand an insulin resistance panel with fasting insulin, glucose, C-peptide, and HOMA-IR, including result patterns, limits, preparation, and follow-up.

An insulin resistance blood test panel combines fasting insulin and glucose with calculated HOMA-IR and, in some panels, C-peptide. The tests show how much...

Insulin/C-Peptide Ratio Test: Exogenous Insulin Use, Insulin Production, and Results

Learn how the insulin/C-peptide molar ratio is calculated and interpreted during hypoglycemia, including exogenous insulin patterns, endogenous secretion, assay limits, and follow-up tests.

The insulin/C-peptide ratio is a calculated laboratory value used mainly during the investigation of documented hypoglycemia. Insulin and C-peptide are released together when the...

Leptin Blood Test: High, Low, Obesity, Metabolic Health, and Results

Understand what a leptin blood test measures, why levels may be high or low, how obesity and leptin resistance affect results, and when specialized follow-up is appropriate.

A leptin blood test measures a hormone made mainly by fat cells that helps the brain assess long-term energy stores. Leptin usually rises as...