Remember both NAM and Niacin increases glucose.
Yes but only with long term use:
"According to the information I found, there is evidence suggesting that long-term niacin treatment can induce insulin resistance. Studies have shown that while niacin initially decreases the plasma concentration of free fatty acids, it can lead to a normalization of plasma nonesterified fatty acid (NEFA) levels and induce insulin resistance over time [2][3]. The underlying mechanisms for this effect are not yet fully understood. It is important to note that these studies focused on the long-term effects of niacin treatment and not the short-term or acute effects.
Additionally, it is worth mentioning that niacin can cause hyperglycemia (high blood sugar) and abnormal glucose tolerance, as well as glycosuria (sugar loss in the urine) [5]. Therefore, individuals taking niacin, especially in high doses, may need to monitor their blood glucose levels more closely and adjust their diabetes medications if necessary." (chatGPT)