Evidence-Based Supplement & Herb Guides

Low-Dose Dexamethasone Suppression Test: Cushing Syndrome Screening and Results

Understand the 1-mg low-dose dexamethasone suppression test, the common cortisol cutoff of 1.8 mcg/dL, causes of nonsuppression, and the follow-up used for Cushing screening.

The low-dose dexamethasone suppression test checks whether a small dose of synthetic glucocorticoid can turn down the body’s cortisol production. It is one of...

Morning Cortisol Test: Low Levels, Adrenal Insufficiency, and Results

Learn how an 8–9 a.m. cortisol test screens for adrenal insufficiency, what low and intermediate results mean, how ACTH helps identify the cause, and when stimulation testing is needed.

A morning cortisol test measures cortisol near the time it should naturally be highest, usually between 8 and 9 a.m. It is often the...

Pheochromocytoma and Paraganglioma Test Panel: Metanephrines, Normetanephrine, Catecholamines, and Results

Learn how a pheochromocytoma and paraganglioma panel uses plasma or urine metanephrines, normetanephrine, catecholamines, and controlled collection to interpret abnormal results.

A pheochromocytoma and paraganglioma test panel looks for biochemical evidence of tumors that produce catecholamines or their metabolites. Pheochromocytomas arise in the adrenal medulla,...

Plasma Catecholamines Test: Epinephrine, Norepinephrine, Dopamine, and Results

Learn what plasma epinephrine, norepinephrine, and dopamine results mean, why collection posture matters, common causes of high values, and when metanephrine testing is preferred.

A plasma catecholamines test measures epinephrine, norepinephrine, and dopamine in a blood sample. These fast-acting chemicals help control heart rate, blood pressure, blood flow,...

Plasma Free Metanephrines Test: Pheochromocytoma and Paraganglioma Screening, High Levels, and Results

Learn how plasma free metanephrine and normetanephrine testing screens for pheochromocytoma and paraganglioma, why supine rest matters, and how high or borderline results are evaluated.

A plasma free metanephrines test measures metanephrine and normetanephrine in blood to screen for pheochromocytoma and paraganglioma. These rare tumors arise from chromaffin tissue...

Plasma Normetanephrine Test: High Levels, Pheochromocytoma Screening, and Results

Learn what a high plasma normetanephrine result means, why supine rest matters, common false-positive causes, when clonidine testing is used, and how PPGL evaluation proceeds.

A plasma normetanephrine test measures a stable metabolite of norepinephrine and is used mainly to screen for pheochromocytoma and sympathetic paraganglioma. These tumors can...

Primary Aldosteronism Test Panel: Aldosterone, Renin, Potassium, ARR, and Results

Learn how aldosterone, renin, potassium, and the ARR screen for primary aldosteronism, how medicines affect results, and when confirmation, CT, or adrenal vein sampling is needed.

A primary aldosteronism test panel measures aldosterone, renin, potassium, and the aldosterone-to-renin ratio, or ARR, to look for inappropriate aldosterone production. Aldosterone helps the...

Renin Blood Test: High, Low, Normal Range, Aldosterone Ratio, and Results

Learn what high or low renin means, how PRA differs from direct renin, how aldosterone and potassium complete the pattern, and why medicines and posture affect the ARR.

A renin blood test measures activity in the kidney-controlled system that regulates blood pressure, sodium, potassium, and fluid balance. Renin rises when the kidneys...

Salivary Cortisol Test: Cortisol Rhythm, Cushing Screening, Stress Hormone, and Results

Learn how salivary cortisol reflects the daily rhythm, when late-night testing screens for Cushing syndrome, why stress panels have limits, and what high, low, or flat results may mean.

A salivary cortisol test measures free cortisol that has moved from blood into saliva. It can be collected at home without a needle, making...

Urine Catecholamines Test: Adrenal Tumor Screening and Results

Learn how a 24-hour urine catecholamines test measures epinephrine, norepinephrine, and dopamine, why collection quality matters, and when metanephrine testing is preferred.

A urine catecholamines test measures epinephrine, norepinephrine, and dopamine excreted during a timed collection, usually 24 hours. It can help evaluate a suspected catecholamine-producing...

22q11.2 Deletion Syndrome Genetic Test: DiGeorge Syndrome and Results

Learn how 22q11.2 deletion syndrome genetic testing works, what positive, negative, prenatal, and family results mean, and which follow-up evaluations may be needed.

A 22q11.2 deletion syndrome genetic test looks for a missing segment of chromosome 22. The deletion can affect the heart, palate, immune system, calcium...

Amniocentesis Genetic Test: Chromosomes, DNA, Diagnosis, and Results

Understand how amniocentesis tests fetal chromosomes and DNA, when it is offered, how the procedure works, what results mean, and the risks and alternatives.

Amniocentesis is a prenatal diagnostic procedure that removes a small amount of amniotic fluid for laboratory testing. The fluid contains fetal cells and other...

Cell-Free DNA (cfDNA) Prenatal Test: Fetal Chromosome Screening and Results

Learn how cell-free DNA prenatal screening works, what low-chance, high-chance, no-call, and atypical results mean, and when CVS or amniocentesis is needed.

Cell-free DNA prenatal testing is a blood screening test that estimates the chance of selected fetal chromosome conditions, especially trisomy 21, trisomy 18, and...

CFTR Genetic Test for Male Infertility: Congenital Absence of the Vas Deferens and Results

Learn how CFTR testing helps diagnose congenital absence of the vas deferens, how to read results, why partner testing matters, and which fertility options are available.

A CFTR genetic test can help explain male infertility caused by congenital absence of the vas deferens, the tubes that normally carry sperm from...

Chorionic Villus Sampling (CVS) Genetic Test: Prenatal Diagnosis and Results

Learn how chorionic villus sampling provides early prenatal diagnosis, how CVS is performed, what normal, abnormal, uncertain, and mosaic results mean, and when amniocentesis may be needed.

Chorionic villus sampling, or CVS, is an early prenatal diagnostic procedure that collects a small sample of placental tissue for chromosome or DNA testing....

Down Syndrome Genetic Test: Trisomy 21 Screening, Diagnosis, and Results

Understand Down syndrome genetic testing, including trisomy 21 screening, CVS and amniocentesis diagnosis, chromosome results, recurrence, and next steps.

A Down syndrome genetic test can estimate the chance that a pregnancy is affected by trisomy 21 or confirm whether an extra copy of...

Edwards Syndrome Genetic Test: Trisomy 18 Screening, Diagnosis, and Results

Learn how Edwards syndrome genetic testing screens for and diagnoses trisomy 18, how results are reported, and what they mean for care and recurrence.

An Edwards syndrome genetic test looks for extra chromosome 18 material, a finding called trisomy 18. During pregnancy, some tests estimate the chance of...

Embryo Genetic Testing: IVF, Chromosomes, Mutations, and Results

Understand embryo genetic testing in IVF, including PGT-A, PGT-M, PGT-SR, biopsy, mosaic results, limitations, embryo transfer, and prenatal confirmation.

Embryo genetic testing examines a small group of cells from embryos created through in vitro fertilization. The test can look for extra or missing...

Fetal Aneuploidy Test: Trisomy, Monosomy, Chromosome Risk, and Results

Understand fetal aneuploidy testing for trisomy, monosomy, chromosome risk, screening results, diagnostic confirmation, mosaicism, and next steps.

A fetal aneuploidy test evaluates whether a pregnancy may have an extra or missing chromosome. An extra copy is called a trisomy; a missing...

First-Trimester Screening Test: Down Syndrome Risk, PAPP-A, hCG, and Results

Understand first-trimester screening for Down syndrome risk, including PAPP-A, hCG, nuchal translucency, result ratios, limitations, and follow-up options.

First-trimester screening combines an ultrasound measurement with pregnancy-related blood markers to estimate the chance of Down syndrome and, in many programs, trisomy 18 and...