Inclusion criteria:
Age of at least 35 years
Patients with type 2 diabetes who are treated with insulin or combined therapy (insulin with antidiabetic pill)
They have NPDRP without the need for specific ophthalmologic treatment interventions
HbA1C levels below 8%
Systolic blood pressure up to 130
Diastolic blood pressure is up to 80 mmHg
Normal GFR is proportional to age based on MDRD formula
The amount of 24-hour urine albumin is less than 300 milligrams.
Exclusion criteria:
The history of any ocular disease (glaucoma, hypertensive retinopathy and cataract), or the history of eye surgery, or previous intra-ocular injections or visual acuity less than 6/10
History of chronic disease such as sarcoidosis, hyperparathyroidism and seizure, bone cancer or lung and liver cirrhosis and...
History of bariatric surgery or absorption disorders or any other disease indicating vitamin D intake.
History of kidney stones
Pregnancy and lactation
History of taking phenofibrate, thiazolidinedione, anticonvulsants, or drugs that interfere with the metabolism of vitamin D or produce eye effects, including macular edema.
The history of severe psychiatric illnesses such as schizophrenia, mood disorders, borderline disorders.
Regular supplementation of D supplementation in the last three months or during the study (in the control group)
History of any drug allergy or side effects.
Participants are reluctant to take drugs or placebo
Participate in another research project over the past 3 months
HbA1C levels of 8% and more
Glucocorticoid intake in the last 3 months
BMI more than 35
The amount of 24-hour urine albumin exceeds 300 milligrams
The GFR is greater than the normal range based on the age-appropriate MDRD formula.