Is tTG IgA useful for blood sugar?

The question about tTG IgA and blood sugar is medically unusual. tTG IgA (tissue transglutaminase antibodies) is a well-established screening marker for celiac disease, not directly for blood sugar. An indirect link exists: untreated celiac disease can cause malabsorption and glucose intolerance, and celiac prevalence is higher in type 1 diabetes. However, tTG IgA is not a blood sugar test. The provided contexts contain no information on tTG IgA or blood sugar. Evidence is therefore 'unclear', based on general medical knowledge. For blood sugar assessment, fasting glucose, HbA1c, or oral glucose tolerance test (OGTT) are appropriate. Measuring tTG IgA without suspicion of celiac disease is not indicated. Note: For symptoms like fatigue or weight gain, a physician should be consulted to determine proper diagnostics.