Blood work guides

In-depth, sourced guides to the blood tests people order most: what to test, when, and what the results mean. Every clinical number links to its source.

GLP-1 Blood Work: Labs Before and During Semaglutide or TirzepatideBefore starting semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound), most clinicians check an A1c, a metabolic panel for kidney and liver function, a lipid panel and a CBC. With diabetes, the ADA advises rechecking A1c about every 3 months after a treatment change and at least twice a year once stable. Kidney tests matter most if vomiting or diarrhea causes dehydration. Routine calcitonin testing is not advised.TRT Blood Work: Which Labs to Check, When, and What the Numbers MeanTRT blood work starts with two fasting morning total testosterone tests, plus LH/FSH, hematocrit and, for many men over 40, PSA. Guidelines then recheck testosterone and hematocrit 3–6 months after starting, and again every year. On weekly or biweekly injections, testosterone is drawn midway between doses. A hematocrit above 54% means therapy is paused.Annual Blood Work: Which Tests to Get by Age and Sex (and What Physicals Miss)Most healthy adults need fewer yearly blood tests than they think, plus a few that physicals often skip. Guidelines back a lipid panel, diabetes screening (A1c or fasting glucose) from age 35, and HIV and hepatitis C screening. Commonly missed: a once-in-a-lifetime Lp(a) test, ferritin with heavy periods, and kidney checks with diabetes or high blood pressure.How to prepare for a blood testFasting, coffee, water, exercise and more: what can skew your result.