Question: Can intense itching be a side effect for someone with diabetes whose blood sugars are poorly controlled?
Answer: Poorly controlled diabetes is one possible cause for unexplained itching. Exactly how diabetes causes itching isn't certain, but suggested causes include diabetic nerve root injury, metabolic abnormalities from widely fluctuating blood sugars, and dry skin. If this is the cause, it should improve with better efforts to lower the blood sugars.
That said, there are many other causes for severe itching. Dry skin from eczema is a common cause that's fairly easy to treat with moisturizers and steroid cream/ointment. Cholestatic liver disease with high blood levels of bilirubin is another cause of severe itching. A normal set of liver enzyme tests will rule this out. Either a very slow or a very fast thyroid can cause itching, so be sure to check thyroid function. Severe chronic kidney failure can also cause itching from the buildup of toxins. High levels of circulating blood histamines from a tumor can cause itching, so be sure to check a blood histamine level. Folks who have a disorder called polycythemia vera may experience itching due to high circulating levels of histamine-producing mast cells.