In theory it could have a very small impact by diluting the blood but I wouldn't think that it was significant, especially if you test soon after drinking the water.
Being well hydrated makes it easier for the phlebotomist to access a vein, so I drink water before my fasting tests at the surgery.
For fasting blood sugar at home I test as soon as I wake up so nothing taken by mouth beforehand.
Being well hydrated makes it easier for the phlebotomist to access a vein, so I drink water before my fasting tests at the surgery.
For fasting blood sugar at home I test as soon as I wake up so nothing taken by mouth beforehand.