Higher levels of a hormone called FGF-21 in the blood are linked to worse blood sugar control in adults — both right after eating and over time.

What we've found so far is that higher levels of the hormone FGF-21 in the blood are linked to poorer blood sugar control in adults. This includes blood sugar levels both after meals and over longer periods of time [1]. Our analysis of the available research shows that all 42.0 assertions we reviewed support a connection between elevated FGF-21 and worse blood sugar regulation [1]. We did not find any studies that contradict this pattern. While we don’t yet know whether FGF-21 is directly involved in raising blood sugar or is simply a marker of underlying metabolic issues, the link appears consistent across the evidence we’ve examined so far. It’s important to note that our current analysis only reflects what has been reported in these assertions. We are not saying FGF-21 causes higher blood sugar — only that higher levels of it tend to appear alongside poorer blood sugar control. The exact role FGF-21 plays in metabolism remains unclear, and more research may help clarify whether this hormone is a response to, or a contributor to, changes in blood sugar. We also want to be clear that our understanding is based on a limited number of assertions — just one unique claim repeated across 42.0 studies or analyses. That means while the direction of the evidence is consistent, the diversity of evidence is low. We can’t yet say how strong or reliable this link is across different groups of people or under different conditions. For now, what this means is that FGF-21 shows up frequently in discussions about blood sugar regulation, and it may be a signal your body is struggling to manage glucose effectively. But we don’t have enough evidence to say whether measuring or targeting FGF-21 would help improve blood sugar control in everyday life.