Habitual moderate coffee drinking has actually been associated with increased insulin sensitivity and lowered risk for type 2 diabetes. But in acute and high doses, caffeine can decrease insulin sensitivity and raise plasma insulin levels.

Does coffee increase insulin levels?

We found that high coffee consumption for 4 weeks increased fasting insulin concentrations compared with coffee abstinence. Consumption of somewhat weaker coffee and caffeine intake were nonsignificantly associated with higher fasting insulin concentrations.

How much caffeine will spike insulin?

If you already have diabetes, however, the impact of caffeine on insulin action may be associated with higher or lower blood sugar levels. For some people with diabetes, about 200 milligrams of caffeine — or the equivalent of one to two 8-ounce (240-milliliter) cups of plain, brewed coffee — may cause this effect.