PREVALENCE OF VITAMIN B12 DEFICIENCY IN PATIENTS WITH DIABETES ON LONG-TERM USE OF METFORMIN

Abstract

INTRODUCTION
Metformin is one of the first-line medications for diabetes. Previous studies found a correlation between long-term use of metformin and vitamin B12 deficiency. Thus, patients treated with metformin are recommended to undergo periodic testing for vitamin B12 levels by the American Diabetes Association. There are few studies about the prevalence of metformin-associated vitamin B12 deficiency in Thailand. This study aims to determine the prevalence and associated factors of vitamin B12 deficiency among patients with diabetes in one tertiary care Hospital in Thailand.

METHODOLOGY
This is a cross-sectional study. Data were collected from patients with diabetes from 31st March 2018 to 30th August 2020 at the outpatient department of Phramongkutklao Hospital. Twelve-hour fasting blood samples were tested for vitamin B12 level, and the cut-off point for diagnosis of B12 deficiency is less than 200 pg/mL. Factors associated with vitamin B12 deficiency were determined.

RESULTS
All 184 participants met the criteria, and almost 60% were male. The median duration of diabetes was 8 (4, 13) years. The average dose of metformin was 1352.7 ± 645.1 mg/day. Sixty-four patients took vitamin B supplements before the blood test for vitamin B12 levels. There were seven participants (3.8%) diagnosed with metformin-associated with vitamin B12 deficiency. Results showed vitamin B12-deficient patients took 2050 ± 755.5 mg of metformin per day compared to 1325.1 ± 627.1 mg/day (p 0.003) of metformin in those with normal vitamin B12 levels. In addition, age and metformin dosage were associated with vitamin B12 deficiency with adjusted odds ratio of 1.1 (1.0- 1.3) and 1.1 (1.0-1.2), respectively.

CONCLUSION
The prevalence of metformin-associated vitamin B12 deficiency is less than 5% in Phramongkutklao Hospital. We suggest against routinely checking for vitamin B12 levels in patients with diabetes who are currently on metformin unless there are clinical indications of deficiency.