Higher levels of a hormone called FGF-21 in the blood are linked to the liver not responding well to insulin in adults — meaning the liver may be struggling to manage blood sugar properly.

What we've found so far is that higher levels of a hormone called FGF-21 in the blood are linked to reduced liver response to insulin in adults [1]. This means the liver may not be managing blood sugar as effectively when FGF-21 levels are elevated. Our analysis of the available research shows that all 42.0 studies we reviewed support a connection between higher FGF-21 levels and liver insulin resistance [1]. Insulin resistance means the body’s cells, including those in the liver, do not respond well to insulin, which can make it harder to control blood sugar. The liver plays a key role in releasing and storing glucose, so when it becomes resistant to insulin, blood sugar regulation can be affected. We don’t yet know whether high FGF-21 levels are a cause, a result, or simply a marker of this insulin issue. FGF-21 is involved in how the body handles energy and metabolism, and its rise may reflect the body’s attempt to cope with metabolic stress [1]. Still, based on what we’ve reviewed so far, the evidence consistently points to a link. There are no studies in our current analysis that refute this pattern, but that doesn’t mean the picture is complete. More research may change how we interpret these findings over time. Practical takeaway: If you have concerns about blood sugar control or liver health, paying attention to metabolic markers — possibly including FGF-21 in the future — might offer insights, but we’re not ready to use this hormone as a clear diagnostic tool yet.