The purpose of this study is to determine the association between serum 25-hydroxyvitamin D and HbA1c levels in diabetic patients with chronic kidney disease. The investigators hypothesized that serum 25-hydroxyvitamin D levels were negatively correlated with HbA1c levels.

This was a cross sectional study using consecutive sampling methodology for participant recruitment. It was carried out at the specialized diabetic, renal, and general outpatient clinics in the University of Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia.

Serum 25(OH)D levels were determined by using direct chemiluminesent immunoassay (ADVIA Centaur XP; Siemens Healthcare Diagnostics, Tarrytown, New York, USA). Serum HbA1c levels were determined using high-pressure liquid chromatography (Variant™ II Turbo; Bio-Rad, Hercules, California, USA).

Data collected will be analyzed using Statistical Package for Social Sciences SPSS version 23.0 for Windows, version 23.0 (IBM Corp., Armonk, New York, USA).

Inclusion Criteria:

• eGFR 15-59 ml/min/1.73m2
• age ≥ 18 years old
• able to provide informed consent

Exclusion Criteria:

• active infections
• autoimmune diseases
• malignancies
• on immunosuppressive therapy
• on vitamin D supplements

Patients who attended specialized diabetic, renal, and general outpatient clinics in the University of Malaya Medical Centre (UMMC), Kuala Lumpur, Malaysia.

A dataset of participants' clinical characteristics and biochemical tests result. The data was obtained directly from the participants and via Laboratory Information System. It is ready for submission.