Hba1c was found 6.1 and vitamin d level was found less than 5ngm/ml. does taking vitamin d supplements cures my case of being prediabete. thx?

Vitamin D cure?: Your being pre-diabetic will not be solved by vitamin d supplements. If you have risk factors for diabetes such as obesity, poor diet and lack of exercise, modification of those will be better than taking vitamin d. As your vitamin d2 level is low, supplemental vitamin d is needed and not for the prevention of diabetes. Speak to your physician about your problem.

Do it anyway: It actually may help, but do it for your own sake. Today's "healthy lifestyles" (limited diet, lack of sunlight) has created an epidemic of vitamin d deficiency. Try to keep your glucose tolerance up by getting back into the intense aerobic-fitness-focused lifestyle you cherished as a teen. Best wishes.

No: They are separate issues. You still would have to follow your diet and exercise and weight loss if advised to avoid development of diabetes and take the vit d supplement given by your doctor.