Welcome to Carnivore Talk Wes. In answer to your question, there can be many factors that could contribute to this. Normal biological variation - Fasting insulin is not as stable as many people think. Day-to-day fluctuations occur. Different laboratory methods - If the tests were run by different labs or different assay methods, results can vary. Stress or poor sleep before the blood draw can increase insulin levels. Illness, inflammation, or infection around the time of testing can temporarily raise insulin. Weight gain since the prior test could contribute. Less physical activity can increase insulin resistance and insulin levels. Certain medications, such as steroids, can raise insulin. Long-term high protein intake can stimulate insulin secretion even when carbohydrate intake is very low. This doesn't necessarily indicate insulin resistance by itself. The more important question is whether your glucose levels changed as well. Fasting insulin by itself is difficult to interpret. Ideally, you would want: Fasting glucose Fasting insulin HbA1c Waist circumference and weight trends Using fasting glucose and fasting insulin together, you can calculate a measure called HOMA-IR, which gives a better picture of insulin sensitivity than insulin alone. HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. It’s a calculation that uses your fasting glucose and fasting insulin to estimate how resistant your body is to insulin. The formula most commonly used in the United States is: Less than 1.0: Excellent insulin sensitivity 1.0–1.9: Normal 2.0–2.9: Early insulin resistance may be present 3.0 or higher: Suggests significant insulin resistance These are rough guidelines, and interpretation can vary somewhat depending on the lab and the person’s overall health. Example If someone has: Fasting insulin = 16.6 μIU/mL Fasting glucose = 95 mg/dL Then: HOMA-IR = (16.6 × 95) ÷ 405 = 3.9 That would suggest insulin resistance despite a normal fasting glucose. One thing to keep in mind: people following a very low-carbohydrate or carnivore diet sometimes develop what’s called physiological insulin resistance (also called adaptive glucose sparing), which can make glucose-related measurements look different from someone eating a standard diet. That’s why it’s helpful to look at the whole picture—fasting glucose, fasting insulin, HbA1c, triglycerides, HDL cholesterol, weight, and waist size—rather than a single number. I hope this helps you.