Received: 24.06.2025 Accepted: 07.10.2025 Published online: 31.10.2025
УДК: 616.379-008.64-085.357.2-07:577.161.2
DOI: 10.53511/pharmkaz.2025.5.2
VITAMIN B12 LEVELS IN PATIENTS WITH TYPE 2 DIABETES MELLITUS RECEIVING
METFORMIN: A CROSS-SECTIONAL STUDY (CROSS-SECTIONAL STUDY)
Bolshakova S.¹, Abylaiuly Zh.¹, Imangali A.¹, Serikkanova T.¹, Kabylbekova A.¹
¹Asfendiyarov Kazakh National medical university, Almaty, Republic of Kazakhstan
Background: Type 2 diabetes mellitus (T2DM) remains a global health problem. Metformin is a first-line drug, but with long-term use it can cause vitamin B₁₂ deficiency. Metformin use is thought to interfere with the absorption of the vitamin in the small intestine. B₁₂ deficiency has been associated with neurological and cognitive impairment, particularly in older patients, but research remains inconsistent. Diagnosis is difficult due to the limited information content of the serum B₁₂ level alone; additional markers and age-related factors are suggested. Some experts consider levels below 450 pg/mL to be a relative deficiency in the presence of risk factors.
Objective: To assess the prevalence of vitamin B12 deficiency among patients with established type 2 diabetes mellitus treated with metformin.
Methods: This cross-sectional study was conducted at the Clinic of Internal Medicine of the S.D. Asfendiyarov Kazakh National Medical University among 101 patients with type 2 diabetes mellitus treated with metformin for at least 3 years. All participants had their vitamin B₁₂ levels measured once. Data on the duration of therapy, age, and other factors potentially associated with vitamin B₁₂ deficiency were also analyzed.
Results: The study included 101 patients with type 2 diabetes, the average age was 62 years, the average duration of metformin therapy was 9 years. The median vitamin B₁₂ level was 450 pg/ml. Deficiency (<200 pg/ml) was detected in 2%, insufficiency (200–300 pg/ml) in 19%, relative deficiency (300–450 pg/ml) in 29% of patients, most of whom were over 60 years old. In 39%, the vitamin level was within 451–880 pg/ml, in 11% it exceeded 880 pg/ml.
Conclusions: A significant proportion of patients with type 2 diabetes mellitus taking metformin for a long time, especially those over 60 years of age, have reduced or borderline vitamin B₁₂ levels. This may indicate a risk of subclinical deficiency and the development of neurological and cognitive complications. The results highlight the need for regular monitoring of vitamin B₁₂ in this category of patients.
Keywords: Metformin, vitamin B12, type 2 diabetes mellitus, vitamin B12 deficiency, side effects, cognitive impairment.
