Section
Labs
16 pages in this section, most recently updated September 4, 2026. Each opens with a plain-English summary and cites its sources.
01 · Labs
FeaturedHemoglobin A1c on GLP-1 therapy: what it measures, the cut points, and how often it is repeated
You'll get: A1c shows your average blood sugar over about three months. It does not need fasting.
A1c is the three-month average of blood glucose. Why it is drawn before semaglutide or tirzepatide, the diagnostic cut points from MedlinePlus and the ADA, the ADA repeat schedule, and the conditions that make the number unreliable.
Updated September 4, 2026
02 · Labs
Fasting glucose: the single-moment number, the 70 to 99 range, and the hypoglycemia threshold in the labels
You'll get: Fasting glucose is a one-moment reading after eight hours without food. Normal is 70 to 99.
What a fasting plasma glucose adds to an A1c, the MedlinePlus normal range of 70 to 99 mg/dL, the ADA diagnostic cut points, and the 54 mg/dL hypoglycemia definition that appears in the Wegovy label for people also taking insulin or a sulfonylurea.
Updated September 4, 202603 · Labs
Lipid panel on GLP-1 therapy: total, LDL, HDL and triglycerides, the healthy levels, and when to repeat
You'll get: A lipid panel is total cholesterol, LDL, HDL and triglycerides. None is a GLP-1 monitoring requirement.
What the four numbers on a lipid panel mean, the healthy levels for adults from MedlinePlus, why prescribers draw one before semaglutide or tirzepatide, what the SELECT trial did and did not show about cardiovascular risk, and the ADA intervals for repeating it.
Updated September 4, 202604 · Labs
FeaturedComprehensive metabolic panel (CMP): the 14 tests, their common ranges, and what each one is doing on a GLP-1 baseline
You'll get: The CMP is 14 tests from one tube: blood sugar, kidney function, salts, liver enzymes and proteins.
The CMP bundles glucose, kidney function, electrolytes, liver enzymes and proteins into one draw. What each of the 14 results means, the MedlinePlus ranges, why it is the standard baseline before semaglutide or tirzepatide, and which parts the labels ask prescribers to re-check.
Updated September 4, 202605 · Labs
FeaturedKidney function on GLP-1 therapy: creatinine, eGFR, the KDIGO categories, and the label's dehydration warning
You'll get: Creatinine and eGFR are the two kidney numbers on every metabolic panel.
Creatinine and eGFR are the two kidney numbers on every metabolic panel. The MedlinePlus creatinine range, the KDIGO 2024 eGFR categories, why every semaglutide and tirzepatide label tells prescribers to monitor renal function during vomiting or dehydration, what the FLOW trial showed, and the ADA annual screening rule for diabetes.
Updated September 4, 202606 · Labs
Liver enzymes on GLP-1 therapy: ALT, AST, ALP and bilirubin, the ranges, fatty liver, and the Wegovy MASH indication
You'll get: Liver enzymes come with the metabolic panel. They are often mildly raised before therapy because of fatty liver, not the drug.
What the four liver tests on a metabolic panel measure, the MedlinePlus ranges, why a mildly raised ALT is common before therapy, what the Wegovy label's MASH indication says and does not say, and how often liver enzymes are repeated.
Updated September 4, 202607 · Labs
TSH and the thyroid on GLP-1 therapy: what the C-cell warning does and does not mean for testing
You'll get: TSH measures thyroid function. The boxed warning is about a rare thyroid tumour, and TSH does not screen for it.
TSH measures thyroid function; the boxed warning on every semaglutide and tirzepatide label is about a rare thyroid tumor, and TSH does not screen for it. The MedlinePlus TSH range, when a TSH is worth drawing, what happens to levothyroxine as weight and gastric emptying change, and the label sentence on calcitonin and ultrasound.
Updated September 4, 202608 · Labs
FeaturedLipase and amylase on GLP-1 therapy: the label numbers, the pancreatitis warning, and why routine testing is not asked for
You'll get: Lipase and amylase are pancreas enzymes. In trials, both rose on average in people taking these drugs.
The semaglutide and tirzepatide labels report mean rises in amylase and lipase on treatment and state that the clinical significance of an isolated rise is unknown. What the enzymes measure, the MedlinePlus ranges, the exact label figures, the 2014 FDA and EMA pancreatic safety assessment, and when lipase is actually drawn.
Updated September 4, 202609 · Labs
Vitamin B12 on GLP-1 therapy: who is at risk, the range, and why metformin is the real reason it is on the panel
You'll get: No GLP-1 label mentions B12. It is on panels because of metformin, acid reducers, vegan diets and past weight-loss surgery.
No GLP-1 label mentions vitamin B12. It appears on panels because of metformin, acid-reducing drugs, vegan diets and past bariatric surgery, and because intake falls when appetite does. The MedlinePlus range, the methylmalonic acid confirmation step, the ADA recommendation for metformin users, and how often to check.
Updated September 4, 202610 · Labs
Vitamin D on GLP-1 therapy: the 25-hydroxy test, the thresholds, and why routine testing is no longer recommended
You'll get: The main expert body now advises against routine vitamin D tests in healthy adults.
The 25-hydroxyvitamin D test, the MedlinePlus and NIH thresholds, the 2024 Endocrine Society guideline that suggests against routine testing in healthy adults, the reasons it still gets ordered in people losing weight, and what the GLP-1 labels say (nothing).
Updated September 4, 202611 · Labs
Iron and ferritin on GLP-1 therapy: reading iron stores when intake drops
You'll get: Ferritin measures stored iron and falls months before a blood count shows anemia.
Ferritin measures iron stores; serum iron, TIBC and saturation describe iron in transit. The MedlinePlus ranges, the WHO ferritin thresholds, why iron comes up when appetite falls or periods are heavy, how inflammation fools ferritin, and how iron connects to the CBC and A1c.
Updated September 4, 202612 · Labs
Complete blood count (CBC) on GLP-1 therapy: hemoglobin, MCV, platelets, and why it sits next to the A1c
You'll get: A blood count checks red cells, white cells and platelets. No GLP-1 label requires it.
A CBC counts red cells, white cells and platelets. The MedlinePlus ranges for each line, what the red cell indices reveal about iron and B12, why anemia matters for A1c interpretation, and the honest answer on how often to repeat it (no label sets an interval).
Updated September 4, 202613 · Labs
Electrolytes and dehydration on GLP-1 therapy: sodium, potassium, bicarbonate, and the pattern the labels ask prescribers to catch
You'll get: Vomiting, diarrhoea and drinking less are the route from a GLP-1 to a kidney injury in the labels.
Vomiting, diarrhea and drinking less are the route from a GLP-1 to an acute kidney injury in the labels. What sodium, potassium, chloride, bicarbonate and magnesium do, their MedlinePlus ranges, the dehydration pattern on a metabolic panel, and which medicines make a fluid-losing week riskier.
Updated September 4, 202614 · Labs
Pregnancy testing on GLP-1 therapy: what the labels say about pregnancy, contraception and the washout
You'll get: No label requires a pregnancy test, and every label says the drugs may cause harm to a fetus. Most prescribers test anyway.
No GLP-1 label requires a pregnancy test, and every one says the drug may cause fetal harm. The hCG test and its MedlinePlus thresholds, the semaglutide 2-month washout before a planned pregnancy, the tirzepatide oral-contraceptive rule, the pregnancy exposure registries, and why prescribers often test anyway.
Updated September 4, 202615 · Labs
Gallbladder imaging on GLP-1 therapy: the label rates, the symptoms that trigger an ultrasound, and why nobody images routinely
You'll get: Gallstones and gallbladder inflammation are named side effects in every label, at about 1 to 2 percent in trials.
Gallstones and gallbladder inflammation are named adverse reactions in every semaglutide and tirzepatide label, with the trial rates. What the labels instruct (gallbladder studies when cholelithiasis is suspected), what an abdominal ultrasound shows, the blood tests drawn alongside it, and why there is no routine scan.
Updated September 4, 202616 · Labs
Calcitonin and the thyroid C-cell warning: what the labels say about testing, in their own words
You'll get: Every label warns about thyroid tumours in rodents. The same labels say not to test calcitonin as a routine.
Every semaglutide and tirzepatide label carries a boxed warning about thyroid C-cell tumors. The same labels say routine calcitonin monitoring and thyroid ultrasound are of uncertain value. What calcitonin measures, the MedlinePlus range, the 50 ng/L figure in the labels, the contraindication that actually matters, and what to report.
Updated September 4, 2026