Intended for healthcare professionals

Practice Rational Testing

Monitoring glycaemic control in patients with diabetes mellitus

BMJ 2018; 363 doi: (Published 20 November 2018) Cite this as: BMJ 2018;363:k4723
  1. Ravinder Sodi, consultant clinical biochemist and honorary lecturer1 2,
  2. Kim McKay, general practitioner3,
  3. Srilatha Dampetla, consultant endocrinologist and diabetologist4,
  4. Joseph M Pappachan, consultant endocrinologist and diabetologist4
  1. 1Department of Blood Sciences, Royal Lancaster Infirmary & Furness General Hospital, University Hospitals of Morecambe Bay NHS Foundation Trust, Lancaster, UK
  2. 2Lancaster Medical School, University of Lancaster, Lancaster, UK
  3. 3McKay and Partners, Wishaw, UK
  4. 4Department of Medicine, Royal Lancaster Infirmary, University Hospitals of Morecambe Bay NHS Foundation Trust, Lancaster, UK
  1. Correspondence to R Sodi, Ravinder.Sodi{at} or ravsodi{at}

What you need to know

  • Be aware of the factors that give rise to a lower, or higher than expected haemoglobin A1c (HbA1c)

  • Discordant HbA1c and glucose results may identify underlying pathology such as a haemoglobinopathy, or occur as a result of anaemia or chronic kidney disease; discuss appropriate investigations with a clinical biochemist or diabetologist

  • Alternatives to HbA1c for monitoring glycaemia in a patient include glucose profiling using quality assured glucose meters, fructosamine, glycated albumin, or total glycated haemoglobin

  • Discuss with the patient ways to monitor treatment for diabetes, so that they are fully empowered to manage their condition

A 73 year old man with obesity and type 2 diabetes mellitus was referred to the diabetes clinic for advice. He had chronic kidney disease stage 3 and chronic anaemia from angiodysplasia of the small intestine. He was on insulin glargine 35 units every night and soluble human insulin 30 units three times daily before main meals. He was referred because of the discrepancy between his high fasting plasma glucose concentrations (16-21 mmol/L) and lower than expected haemoglobin A1c (HbA1c) concentration (49 mmol/mol) (expected with this fasting plasma glucose concentration ~108-140 mmol/mol or 12-15%). Table 1 gives glucose and HbA1c reference intervals. Other selected blood tests were: haemoglobin 106 g/L (reference interval: 125-180), ferritin 315 µg/L (reference interval: 24-250), creatinine 107 µmol/L (reference interval: 59-104), and albumin 32 g/L (reference interval: 35-50).

View this table:
Table 1

Reference interval for fasting glucose and HbA1c

What is the next investigation?

Monitoring diabetes mellitus

The diagnosis of diabetes mellitus is well described1234; however, the monitoring of diabetes with HbA1c (which is common practice) has introduced some uncertainty. Glycaemic control is integral to effective treatment of diabetes.12 HbA1c concentration is used as the biomarker for long term glycaemic control as it correlates well with average blood glucose levels over a period of 90-120 days …

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