Metformin is considered the first-line treatment in all subjects with type 2 diabetes mellitus (T2DM) not having a contraindication for its use. Patient compliance with metformin is not optimal; however, objective compliance data are scarce. The aim of our study was to analyse the adherence to metformin treatment by determining its plasma levels and to identify its determinants in a broad spectrum of T2DM patients.

In total, 309 patients with T2DM from a single tertiary diabetes centre (mean age 66.5 ± 9.0 years, HbA1C 57.2 ± 13.1 mmol/mol, BMI 30.8 ± 4.9 kg/m2) using standard or XR (sustained release) form of metformin were included in the study. Blood sampling for metformin together with a short questionnaire were performed during a regular outpatient visit. Hydrophilic interaction chromatography and high-resolution mass spectrometry (Q Exactive Plus instrumentation) were used to quantify metformin levels. Values ​​below 100 ng/ml were deemed sub-therapeutic.

Out of 309 patients, sub-therapeutic values were measured in 4.2% and zero levels in 1.9% of subjects. The use of XR form did not increase compliance (16.7 vs. 15.4 vs. 13.8% of subjects for zero vs. sub-therapeutic vs. therapeutic range, n.s.), while all subjects using combination preparation with another antidiabetic agent (11.0%) were in therapeutic range. Zero levels of metformin were associated with a trend to increased HbA1C, higher number of other antidiabetic drugs and more frequent insulin use, whereas age, BMI and diabetes duration had no effect on metformin compliance. Adherence to metformin also increased with education status while not being affected by smoking or alcohol use.

In conclusion, in a tertiary diabetes centre the compliance with metformin treatment was greater than 93% and increased with the use of combination preparations, lower number of antidiabetic drugs and higher education status. The XR form was not associated with increased adherence rate.


I. Lankova: None. I. Miskova: None. S. Frankova: None. D. Kobrova: None. T. Cajka: None. J. Hricko: None. M. Paucova: None. V. Hrádková: None. Z. Vlasakova: None. T. Pelikanova: None. M. Mraz: None. M. Haluzik: Advisory Panel; Self; Lilly Diabetes, Sanofi. Consultant; Self; Ethicon US, LLC. Speaker’s Bureau; Self; AstraZeneca, Mundipharma International, Novartis AG, Novo Nordisk A/S.


Institute for Clinical and Experimental Medicine (00023001); RVOVFN64165

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