The investigators planned to research the effect of vitamin D supplementation on the incidence of contrast-induced nephropathy in patients undergoing coronary angiography.

Vitamin D is primarily generated in the skin, in response to direct absorption of ultraviolet B radiation. Vitamin D can also be obtained through fortified foods and oral supplements. Contrast-induced nephropathy (CIN) is a generally reversible form of acute kidney injury that occurs mostly within 2-3 days of exposure to contrast medium (CM). The estimated incidence of CIN ranges from 2%-50%, and coronary angiography (CAG) or percutaneous coronary intervention (PCI), or both, are associated with CIN in about half of cases. Recently low vitamin D status has been shown to be associated with increased risk of CIN. However, its effects on CIN patients remain unclear. The investigators planned to determine the efficacy of vitamin D on the incidence of contrast-induced nephropathy in patients undergoing coronary angiography. This study may shed light as to whether oral vitamin D supplementation can be an adjunct therapy in CIN patients.

Inclusion Criteria:

• The main inclusion criteria were patients who underwent coronary angiography.

Exclusion Criteria:

• The exclusion criteria were as follows: patients with chronic renal failure, chronic liver disease, bone disorders, and/or thyroid disorders.
• Patients were also excluded if they were taking vitamin D3 tablets or other lipid-regulating drugs.