Metformin has been associated with
lactic acidosis.
Lactate levels are not commonly tested in clinical practice, and it is unclear to what extent
metformin would typically increase
lactate levels with chronic use. The aim of this review was to determine whether regular monitoring of the plasma
lactate level would be beneficial in avoiding
lactate accumulation and, ultimately, minimising the incidence of
lactic acidosis in
metformin-treated patients.A comprehensive search of PubMed, Embase, Web of Science, Cochrane and International Pharmaceutical Abstracts databases covering the period up to 30 May 2017 was performed. Search terms included combinations of terms and keywords, including "
metformin", "
lactate", "
lactic acid" and "
lactic acidosis". Cases series of
lactic acidosis or
metformin-associated
lactic acidosis were excluded.Of 1539 potentially relevant articles, a total of 52 reported
lactate levels from routine/regular pathological tests in
metformin users. The studies were subdivided into four themes, regarding
metformin usage and the reported
lactate levels in patients who: (1) did not have
contraindications to the use of
metformin; (2) had
contraindications, or renal impairment but without other
contraindications; (3) exercised; or (4) also received any
nucleoside reverse transcriptase inhibitor. Studies have reported that
metformin treatment could increase
lactate level of users. However, most results showed that the
lactate level remained in the normal range.No definitive conclusions on the benefits of regular
lactate monitoring in patients taking
metformin can be made. Future research on larger populations focusing on the measurement of
lactate levels with continuous
metformin use is warranted.