5 Blood Markers to Check Before Starting a GLP-1

GLP-1 medications like Ozempic, Wegovy, and Mounjaro can move the numbers fast. But without a baseline, you can't tell whether the medication is helping fix the underlying problem — or just covering it up. These five markers give you a true starting point so you can measure real progress.

Why Get Bloodwork Before Starting a GLP-1?

Whether to take a GLP-1 is a decision between you and your prescriber. This isn't about that choice — it's about understanding your own metabolic health before the medication changes the picture.

A baseline does two things. First, it shows where your metabolism actually stands today. Second, it gives you a reference point to compare against later, so you can see whether your underlying health is improving — not just whether the scale is moving.

Which 5 Markers Matter Most?

1. Fasting insulin. The earliest signal of insulin resistance — often elevated for years before glucose changes.¹ It tells you how hard your body is already working to keep blood sugar in check.

2. HOMA-IR. A simple score that combines insulin and glucose to quantify insulin resistance. Under 1.0 is ideal; above 2.0 means resistance is well established.² This single number captures where you sit on the spectrum.

3. HbA1c. Your average blood sugar over three months. Even within the "normal" range, higher values track with greater long-term metabolic risk,³ so the lower end is the better target.

4. Triglyceride-to-HDL ratio. A quick read on metabolic health from a standard cholesterol panel. Under 2.0 is the goal; higher numbers flag insulin resistance early.⁴

5. GGT. An underused liver marker that reflects oxidative stress and metabolic strain. It rarely makes it onto a routine panel, but it adds valuable context about how hard your liver is working.

What Does Your Baseline Tell You?

Together, these five markers answer a question the scale can't: is your metabolism actually getting healthier? GLP-1 medications often shift weight and glucose quickly, but a true baseline lets you watch whether insulin sensitivity, your lipid pattern, and your liver markers are moving in the right direction too.

It also helps you protect what matters during rapid weight loss — like muscle and nutrient status — so the changes you make are ones you can sustain.

Frequently Asked Questions

Do I need bloodwork before starting a GLP-1?

Your prescriber will guide the medical decision, but a metabolic baseline is valuable for understanding your own health and tracking real progress over time. It's about clarity, not approval.

Which marker is the most important?

Fasting insulin and HOMA-IR are often the most revealing, because they catch insulin resistance years before glucose or HbA1c shift.

Are these tests expensive or hard to get?

Most are inexpensive and widely available. Fasting insulin and GGT are simply ordered less often, so you may need to request them specifically.

How often should I recheck them?

Rechecking every few months is common, which is exactly why a clear baseline matters — it gives you something meaningful to compare against.

References

1. DiNicolantonio, J. J., Bhutani, J., & O'Keefe, J. H. (2017). Postprandial insulin assay as the earliest biomarker for diagnosing pre-diabetes, type 2 diabetes and increased cardiovascular risk. Open Heart, 4(2), e000656. https://doi.org/10.1136/openhrt-2017- 000656
2. Ausk, K. J., Boyko, E. J., & Ioannou, G. N. (2010). Insulin resistance predicts mortality in nondiabetic individuals in the U.S. Diabetes Care, 33(6), 1179–1185. https://doi.org/10.2337/dc09-2110
3. Guo, F., Moellering, D. R., & Garvey, W. T. (2014). The progression of cardiometabolic disease: Validation of a new cardiometabolic disease staging system applicable to obesity. Obesity, 22(1), 110–118. https://doi.org/10.1002/oby.20585
4. Kosmas, C. E., Rodriguez Polanco, S., Bousvarou, M. D., Papakonstantinou, E. J., Peña Genao, E., Guzman, E., & Kostara, C. E. (2023). The triglyceride/high-density lipoprotein cholesterol (TG/HDL-C) ratio as a risk marker for metabolic syndrome and cardiovascular disease. Diagnostics, 13(5), 929. https://doi.org/10.3390/diagnostics13050929

— Michael Rutherford

This article is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, or prescribe, and it is not guidance about whether to start or stop any medication. Always make medical decisions in partnership with a qualified healthcare provider who knows your full history.