10 Essential Biomarkers to Track When Taking GLP-1 Medications

If you’ve been paying attention to health news lately, you’ve probably heard about GLP-1 medications. Drugs like Ozempic, Wegovy, Mounjaro, Rybelsus, and Zepbound have become some of the most talked-about prescriptions in recent years. Originally developed to help people with type 2 diabetes manage blood sugar, these medications are now widely prescribed for weight loss as well. And they work—many people taking GLP-1s see dramatic improvements in their weight, appetite, and even long-term health risks.

But there’s something important that often gets overlooked in the excitement: GLP-1s are powerful drugs that can affect your whole body, not just your appetite or blood sugar. Because of this, it’s crucial to monitor certain health markers, or biomarkers, while taking them. Biomarkers are measurable signals in your body—things like cholesterol levels, liver enzymes, or vitamin levels—that tell doctors how your health is doing behind the scenes.

Monitoring the right biomarkers while on GLP-1s isn’t just about safety. It’s also about getting the most out of these medications. Tracking your labs helps you and your doctor make smarter decisions, catch issues early, and see how your body is really responding.

In this article, we’ll walk through 10 essential biomarkers you should monitor if you’re taking a GLP-1 medication. You’ll learn what each biomarker is, why it matters for GLP-1 users, how often to test, and even what you can do to optimize your numbers. By the end, you’ll have a clear roadmap to help you use GLP-1s safely and effectively—whether your goal is weight loss, better blood sugar control, or long-term health.

Why Biomarker Monitoring Matters on GLP-1s

GLP-1 medications work by mimicking a natural hormone called glucagon-like peptide-1. This hormone has several important jobs: it helps control blood sugar, slows down digestion, and signals to your brain that you’re full. That’s why these medications are so effective for both diabetes management and weight loss.

But here’s the catch: when you change something as central as how your body processes food and blood sugar, other systems in your body get affected too. People on GLP-1s often eat less, lose weight quickly, and experience shifts in metabolism. While many of these changes are positive, they can also bring risks if not carefully managed.

For example, losing weight can sometimes mean losing muscle mass along with fat, which isn’t ideal. Reduced food intake might cause vitamin deficiencies. And because GLP-1s can affect the stomach, liver, kidneys, and even the thyroid, keeping an eye on these organs is important for long-term health.

That’s where biomarkers come in. They’re like health “check engine” lights. By monitoring them, you and your doctor can see whether the medication is working as intended, whether your risk for certain diseases is going up or down, and whether adjustments are needed in your lifestyle, diet, or medication plan.

Now, let’s dive into the 10 most important biomarkers to track if you’re taking a GLP-1.

1. Blood Glucose and Hemoglobin A1C

One of the main reasons GLP-1 medications were created in the first place was to help people lower blood sugar. Blood glucose and Hemoglobin A1C are two of the most important markers here.

Blood glucose tells you the current level of sugar in your bloodstream. It fluctuates throughout the day depending on what you eat, how active you are, and how your body responds to insulin. Hemoglobin A1C, on the other hand, gives a bigger picture. It measures your average blood sugar levels over the past two to three months.

For people with diabetes, these numbers are critical. High glucose and A1C increase the risk of complications like nerve damage, kidney disease, and heart problems. GLP-1 medications usually help lower both, which is one of their greatest benefits. However, in rare cases, blood sugar can drop too low (a condition called hypoglycemia), especially if you’re also taking insulin or another diabetes drug. That’s why monitoring is important: it helps make sure you’re in the healthy range, not too high and not too low.

Doctors usually recommend checking A1C every three months if you have diabetes and at least once a year if you don’t. If you’re new to a GLP-1 medication, more frequent monitoring may be helpful to see how your body is adjusting.

2. Insulin and HOMA-IR

Another key piece of the metabolic puzzle is insulin, the hormone that allows your cells to absorb glucose from your blood. People who are overweight or have type 2 diabetes often have insulin resistance, meaning their bodies need to produce more and more insulin to keep blood sugar under control.

GLP-1 medications can improve insulin sensitivity, which is great news. To measure progress, doctors sometimes look at fasting insulin levels and calculate a score called HOMA-IR (Homeostatic Model Assessment of Insulin Resistance). This score helps reveal how resistant or sensitive your body is to insulin.

Tracking insulin isn’t something every patient does, but it can be incredibly useful, especially if you want to see how your metabolic health is improving beyond just blood sugar numbers. If your insulin levels are dropping while your glucose is staying steady, it’s a sign that your body is becoming more efficient at processing energy—a very good thing for long-term health.

3. Lipid Panel: Cholesterol and Triglycerides

Heart health is another major reason to keep an eye on biomarkers while taking GLP-1s. A lipid panel measures several types of fats in your blood, including LDL cholesterol (“bad” cholesterol), HDL cholesterol (“good” cholesterol), and triglycerides.

GLP-1s can sometimes improve cholesterol and triglyceride levels, particularly as people lose weight and eat less processed food. But that’s not guaranteed, and not everyone responds the same way. Some people might still have stubbornly high cholesterol or other cardiovascular risks even while losing weight.

Since heart disease remains the leading cause of death worldwide, checking your lipid panel regularly—usually once or twice a year—is a smart move. If numbers are off, your doctor can suggest lifestyle changes or medications to protect your heart.

4. Liver Enzymes (ALT, AST, GGT)

Your liver plays a huge role in metabolism, and it’s especially vulnerable in people who are overweight. Many develop fatty liver disease, where fat builds up in the liver and can cause damage over time.

GLP-1 medications may actually help reduce fat in the liver, which is promising. But for some people, liver enzymes like ALT, AST, and GGT can go up while on treatment. These enzymes leak into the blood when liver cells are stressed or damaged, so they serve as a warning sign.

That’s why it’s wise to get liver enzymes checked before starting a GLP-1 and then repeat the test a few months in. If enzymes stay stable or improve, that’s great. If they climb, it’s something your doctor will want to keep an eye on.

5. Kidney Function (Creatinine, eGFR, BUN)

The kidneys are another organ worth monitoring. GLP-1 medications can sometimes cause dehydration due to nausea, vomiting, or reduced food and water intake. Dehydration, in turn, puts stress on the kidneys.

Doctors use blood tests like creatinine, eGFR (estimated glomerular filtration rate), and BUN (blood urea nitrogen) to check how well your kidneys are filtering waste from the blood. For most people, GLP-1s don’t cause kidney problems directly, but if you already have reduced kidney function, extra caution is important.

Even if your kidneys are healthy, testing once or twice a year provides peace of mind and ensures you’re staying safe.

6. Inflammation Marker: hs-CRP

One of the hidden benefits of weight loss and improved metabolic health is a reduction in inflammation. Chronic inflammation is linked to everything from heart disease to arthritis to cancer, and it often improves when people lose weight and eat better.

A biomarker called high-sensitivity C-reactive protein (hs-CRP) is commonly used to measure inflammation in the body. High hs-CRP levels suggest that the body is under stress or fighting ongoing low-grade inflammation.

Tracking hs-CRP while on a GLP-1 can give you a sense of whether your overall inflammation is improving as your weight and metabolic health improve. Lower numbers are generally better, and for many people, GLP-1s help push this marker in the right direction.

7. Electrolytes: Sodium, Potassium, Magnesium

GLP-1 medications often cause digestive side effects like nausea, vomiting, or diarrhea, especially when you first start them. These symptoms can lead to dehydration and electrolyte imbalances.

Electrolytes—minerals like sodium, potassium, and magnesium—are vital for nerve function, heart rhythm, and muscle contraction. Even small imbalances can cause problems like fatigue, muscle cramps, or irregular heartbeat.

Doctors often check electrolytes as part of a basic metabolic panel (BMP) or comprehensive metabolic panel (CMP). If you’ve been dealing with significant side effects or rapid weight loss, it’s particularly important to keep an eye on these numbers.

8. Vitamin B12 and Folate

Since GLP-1 medications suppress appetite, many people end up eating less food overall. While that helps with weight loss, it also raises the risk of nutrient deficiencies. Two vitamins worth paying close attention to are B12 and folate.

Vitamin B12 is important for nerve health, energy, and red blood cell production. Folate plays a role in DNA synthesis and cell growth. Low levels of either can cause fatigue, brain fog, and anemia.

People with diabetes are already at higher risk of B12 deficiency, especially if they take metformin. Adding a GLP-1 medication on top means it’s even more important to check levels and supplement if needed.

9. Thyroid Function (TSH, Free T4, Free T3)

There’s some evidence—still being studied—that GLP-1 medications may affect the thyroid. Animal studies have shown a possible link between GLP-1 drugs and certain thyroid conditions, though this hasn’t been proven in humans.

Even so, it makes sense to check thyroid hormones like TSH, Free T4, and Free T3, especially if you already have a thyroid disorder. Thyroid health is important for metabolism, energy, and weight regulation, so any disruptions could affect your overall progress.

10. Body Composition and Muscle Mass

One of the most exciting but also concerning effects of GLP-1 medications is how they change body composition. These drugs are very effective at reducing body weight, but not all of that weight comes from fat—some comes from lean muscle mass.

Muscle is incredibly important for long-term health. It helps regulate blood sugar, supports mobility, and keeps your metabolism strong. Losing too much muscle can make it harder to maintain weight loss and can even increase risk of frailty as you age.

That’s why monitoring body composition is just as important as tracking weight on the scale. Tools like DXA scans, body impedance tests, or even surrogate markers like albumin and prealbumin can give clues about whether you’re maintaining muscle.

To protect your muscles, focus on eating enough protein and doing resistance training while on a GLP-1. This way, you maximize fat loss while preserving the muscle that keeps your metabolism healthy.

How Often Should You Test These Biomarkers?

The exact frequency depends on your health status and why you’re taking a GLP-1. If you have type 2 diabetes, your doctor may want to check some labs every three months. If you’re taking it primarily for weight loss and you’re otherwise healthy, once or twice a year may be enough.

A good general rule is:

• Baseline testing before starting a GLP-1 medication.
• Follow-up at 3–6 months to see how your body is responding.
• Yearly monitoring for long-term safety, with more frequent checks if something looks off.

The key is to work with your doctor to personalize a testing schedule that fits your needs.

How to Optimize Your Biomarkers While on GLP-1s

Taking a GLP-1 medication isn’t a magic bullet—it works best when combined with healthy habits. If you want your biomarkers to improve as much as possible, focus on a few simple strategies.

Make sure you’re eating enough protein to protect your muscles. Aim for balanced meals with lean meats, fish, beans, or plant-based proteins. Add plenty of fruits, vegetables, and whole grains to keep vitamins, minerals, and fiber in check.

Exercise is another key. Strength training helps preserve muscle mass while you lose fat. Cardio supports heart health and lowers blood pressure. Even walking daily makes a difference.

If your labs show deficiencies, your doctor may suggest supplements—for example, B12, vitamin D, or magnesium. And don’t forget lifestyle factors: quality sleep, stress management, and hydration all play big roles in keeping biomarkers in the healthy range.

When to Talk to Your Doctor

Biomarker monitoring is only useful if you use the information. If you notice unusual results—like rising liver enzymes, declining kidney function, or signs of nutrient deficiency—don’t ignore them. Bring them to your doctor right away.

Sometimes, the fix is as simple as adjusting your diet or taking a supplement. Other times, it might mean changing your medication dose or schedule. Either way, these conversations help keep you safe and ensure you’re getting the best possible results from your GLP-1 treatment.

FAQs

1. Do I really need to test my blood regularly if I’m on a GLP-1?

Yes. Even though GLP-1s are generally safe, they can affect multiple organs. Testing gives you peace of mind and helps prevent problems before they get serious.

2. How do GLP-1 drugs affect cholesterol and heart health?

They often improve cholesterol and triglycerides, but not always. That’s why a yearly lipid panel is recommended.

3. Can GLP-1 medications cause vitamin deficiencies?

Indirectly, yes. Because these drugs reduce appetite and food intake, some people develop low levels of B12, folate, or other nutrients.

4. How do I know if I’m losing too much muscle instead of fat on GLP-1s?

Regular body composition testing helps. If you notice weakness, fatigue, or slower metabolism, it’s a sign you may need more protein and strength training.

5. Are these biomarkers covered by insurance?

Many of them are, especially for people with diabetes or obesity. Coverage varies, so check with your provider.

Conclusion

GLP-1 medications like Ozempic, Wegovy, and Mounjaro are powerful tools for weight loss and diabetes management. But with great power comes responsibility. These drugs can impact many systems in your body, from blood sugar and insulin to your liver, kidneys, and thyroid.

That’s why monitoring biomarkers is so important. By keeping track of the 10 key markers we covered—blood sugar, insulin, cholesterol, liver enzymes, kidney function, inflammation, electrolytes, vitamins, thyroid hormones, and body composition—you can make sure your treatment is safe, effective, and tailored to your needs.

The best part? You don’t have to do it alone. Work with your doctor, ask questions, and use these biomarkers as tools to guide your journey. When combined with smart lifestyle choices, GLP-1 medications can be a game-changer not just for weight loss, but for your long-term health and quality of life.