Lower A1C levels mean that you are better at blood sugar management (33). However, in a study, after giving blood, people with and without type 2 diabetes saw a significant drop (more than 4.28%) in their A1c levels for at least two months. This drop is inaccurate and may make doctors misinterpret that you are managing blood sugar well, while you might not be (34). So, it's important to let your doctor know when your latest blood donation is.