Blood Tests on a GLP-1: What Your Follow-Up Is Checking

Start with the documents that govern the prescription, because they are shorter on this subject than the internet suggests. The Warnings and Precautions sections of the FDA prescribing information for Ozempic (semaglutide, Novo Nordisk, label revised 5/2026), Wegovy (semaglutide, Novo Nordisk, revised 6/2026), Mounjaro (tirzepatide, Eli Lilly, revised 8/2026) and Zepbound (tirzepatide, Eli Lilly, revised 8/2026), all published on DailyMed, contain a small number of explicit monitoring instructions.

All four say to monitor renal function in patients reporting adverse reactions that could lead to volume depletion, especially during dosage initiation and escalation. The Wegovy label (section 2.1 and its hypoglycemia warning) and the Zepbound label (its hypoglycemia warning, section 5.7) say to monitor blood glucose in patients with diabetes before starting and during treatment. All four say that patients with a history of diabetic retinopathy should be monitored for progression. The Wegovy label adds a heart-rate instruction: monitor heart rate at regular intervals consistent with usual clinical practice.

That is the list. It does not include a routine pancreatic enzyme panel, a thyroid ultrasound or a calcitonin level, and the sections below explain why the labels say what they say about each of those. Everything else on your requisition — a metabolic panel, liver enzymes, a lipid profile, an HbA1c on a fixed schedule — comes from your prescriber's judgment about your history, your other conditions and your other medications, and it is fair to ask them what each test is for.

The renal instruction exists because of dehydration, not because the medicines act on the kidney directly. Section 5.6 of the Ozempic label and section 5.5 of the Mounjaro label describe postmarketing reports of acute kidney injury, in some cases requiring hemodialysis, and state that the majority occurred in patients whose nausea, vomiting or diarrhea led to dehydration. The instruction that follows is the one your prescriber is acting on: monitor renal function in patients reporting adverse reactions that could lead to volume depletion, especially during dosage initiation and escalation.

The Mounjaro label goes one step further in section 8.6, saying that no dosage adjustment is recommended for renal impairment but that renal function should be monitored when initiating or escalating in patients with renal impairment who report severe gastrointestinal reactions. The patient-facing Medication Guide for Ozempic puts the same idea in plain language: diarrhea, nausea and vomiting may cause a loss of fluids, which may cause kidney problems, and patients should tell their healthcare provider right away if those symptoms do not go away.

So a creatinine or eGFR result is being read against a question: how much fluid did this person lose, and when? A number from a quiet month and the same number from a fortnight of vomiting are different findings. That is why the dates of your gastrointestinal symptoms, how long each episode lasted and roughly how much you were drinking belong in the record you bring, and why how much water to drink on a GLP-1 is a fair question for the same appointment.

Ozempic is indicated, in the words of its label, as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus, and the clinical studies section of that label reports the trial results as reductions in HbA1c. If you are prescribed a GLP-1 receptor agonist for type 2 diabetes, HbA1c is the measure the indication is built on, and your prescriber will have a view on how often to repeat it that comes from diabetes care standards rather than from the drug label.

For the weight-management products, the instruction is narrower. Section 2.1 of the Wegovy label says that in patients with diabetes mellitus, blood glucose should be monitored prior to starting and during treatment, and the Zepbound label repeats this in its hypoglycemia warning. The reason is in section 5.5 of the Ozempic label and section 5.3 of the Mounjaro label: patients taking these medicines together with insulin or an insulin secretagogue such as a sulfonylurea may have an increased risk of hypoglycemia, including severe hypoglycemia, and the labels say the risk may be lowered by a reduction in the dose of the insulin or secretagogue. That reduction is a prescriber's decision, which is why the label instructs clinicians to inform patients on those medications and educate them on the signs and symptoms.

If you do not have diabetes, the labels contain no glucose-monitoring instruction for you, although the Zepbound label notes that hypoglycemia has also been associated with tirzepatide and GLP-1 receptor agonists in adults without type 2 diabetes. If you do have diabetes, bring your meter readings or your monitor's report, because a single laboratory glucose value is a snapshot and the trend is what the visit is about. The condition itself is covered on GLP-1 for type 2 diabetes.

This is the test people most often expect and the one the labels are most careful about. Each label reports what happened to pancreatic enzymes in its trial program, in the laboratory abnormalities part of section 6.1. The Ozempic label reports a mean increase from baseline in amylase of 13% and lipase of 22% in placebo-controlled trials, changes not observed in placebo-treated patients. The Wegovy label reports mean increases in amylase of 15% to 16% and lipase of 39% in weight-reduction trials. The Mounjaro label reports mean increases in pancreatic amylase of 33% to 38% and lipase of 31% to 42%, against a 4% amylase rise and no lipase change on placebo. The Zepbound label reports amylase increases of 20% to 25% and lipase of 28% to 35%, against 2.1% and 5.8% on placebo.

The Wegovy, Mounjaro and Zepbound labels then add the same sentence: the clinical significance of elevations in lipase or amylase is unknown in the absence of other signs and symptoms of pancreatitis. The Ozempic label reports the enzyme increases without that sentence, and, like the other three, contains no instruction to monitor lipase or amylase. None of the four labels instructs routine lipase or amylase monitoring. The pancreatitis warning — section 5.2 of the Ozempic label, with matching sections in the others — is built around observation instead: after initiation, observe patients carefully for signs and symptoms of acute pancreatitis, which may include persistent or severe abdominal pain, sometimes radiating to the back, with or without nausea or vomiting, and if pancreatitis is suspected, discontinue the medicine and initiate appropriate management.

Two practical consequences follow. First, a mildly raised lipase on a routine panel, in a person with no abdominal pain, is a result the Wegovy, Mounjaro and Zepbound labels describe as of unknown significance, and interpreting it is your prescriber's job, not yours and not this page's. Second, the thing the label does want reported is a symptom, so if you have had abdominal pain that was persistent or severe, the date, duration and location of that pain is more useful to the visit than any enzyme value.

Every one of these products carries a boxed warning about thyroid C-cell tumors. The Ozempic label states that semaglutide causes thyroid C-cell tumors in rodents, that it is unknown whether it does so in humans, and that the product is contraindicated in people with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2. What it does not do is ask for blood tests. Section 5.1 of the Ozempic, Wegovy, Mounjaro and Zepbound labels says that routine monitoring of serum calcitonin or thyroid ultrasound is of uncertain value for early detection of medullary thyroid carcinoma, and that such monitoring may increase the risk of unnecessary procedures because of the low specificity of the calcitonin test and the high background rate of thyroid disease. The labels ask instead that patients be told the symptoms of thyroid tumors — a mass in the neck, difficulty swallowing, shortness of breath, persistent hoarseness — and report them. If a calcitonin result does appear on your form, the reason is specific to you and worth asking about.

The eye instruction is different because it is a monitoring instruction. Section 5.3 of the Ozempic label reports that in a two-year trial in patients with type 2 diabetes and high cardiovascular risk, diabetic retinopathy complications occurred in 3.0% of Ozempic-treated patients compared with 1.8% on placebo, and that the absolute risk increase was larger in people who had retinopathy at baseline (8.2% versus 5.2%) than in those who did not (0.7% versus 0.4%). The label links this to the known temporary worsening of retinopathy that can follow rapid improvement in glucose control, and says that patients with a history of diabetic retinopathy should be monitored for progression. The Mounjaro label, section 5.7, carries the same instruction. That monitoring is an eye examination rather than a blood draw, and the patient counseling section of the Ozempic label asks patients to contact their physician if they experience changes in vision during treatment.

Bloodwork is one input. A typical GLP-1 follow-up reads it alongside several others, and the labels shape those too.

Weight, as a trend rather than the reading on the clinic scale that morning. Gastrointestinal tolerability, because the labels describe nausea, vomiting, diarrhea and constipation clustering during dosage initiation and escalation, and because those symptoms are the bridge to the renal question above. Fluid intake through any rough patches. Heart rate, which the Wegovy label asks clinicians to monitor at regular intervals and which its section 5.9 says should prompt discontinuation if a sustained increase in resting heart rate occurs. Any change to other medications, since section 7 of the Wegovy label notes that delayed gastric emptying can affect the absorption of oral medicines and suggests increased clinical or laboratory monitoring for those with a narrow therapeutic index. And the practical layer: whether doses were taken on schedule, whether supply has been reliable, and whether there is a planned procedure or a period of illness ahead.

The questions you bring belong on a different page, and questions to ask at your GLP-1 follow-up covers them. This page is about the tests and the record. The two work together: a question about a result lands better when the record explaining it is already on the desk.

The results arrive in the clinician's inbox before you do. What they cannot see is the month that produced them, and that is the part you supply.

Bring dose dates for the window since the last visit, including anything missed or delayed, because escalation timing is the context the renal instruction is written around. Bring the weight trend, ideally as a smoothed line or weekly averages rather than every morning's number. Bring a dated symptom log: which days had nausea, vomiting or diarrhea, how long each episode lasted, and any abdominal pain with its location and duration, since those are the symptoms the labels ask about by name. Bring a rough fluid record for the bad days. Bring your glucose readings if you have diabetes, your current list of all other medicines including anything over the counter, and any vision change or thyroid symptom you noticed, however minor it seemed. The format is described step by step in how to prepare a GLP-1 summary for your doctor.

This is the part GLP-1 Tracker is built for. The app keeps dose dates and injection sites, smooths weight into a trend, holds meals and protein, and stores dated notes on how you felt, all on the iPhone in your pocket and free to use. It stores no laboratory values, cannot interpret a result, does not know which tests were ordered or why, and never decides whether anything is normal. Its educational medication-level view is an illustration drawn from what you logged, not a measurement of anything in your blood, and it should not be presented as clinical data. The results are the clinician's. The month that explains them is yours to bring.