Gestational diabetes mellitus

Last reviewed: 28 Dec 2022
Last updated: 30 Mar 2022



History and exam

Key diagnostic factors

  • presence of risk factors (usually asymptomatic)
More key diagnostic factors

Other diagnostic factors

  • polyuria
  • polydipsia
  • fetal macrosomia in a previous pregnancy
Other diagnostic factors

Risk factors

  • elevated BMI
  • previous gestational diabetes
  • previous macrosomic baby
  • family history of diabetes mellitus
  • non-white ancestry
  • advanced maternal age (>40 years)
  • polycystic ovarian syndrome (PCOS)
More risk factors

Diagnostic investigations

1st investigations to order

  • oral glucose tolerance test (OGTT)
More 1st investigations to order

Investigations to consider

  • random blood (plasma) glucose
  • HbA1c
  • fasting plasma glucose (FPG)
More investigations to consider

Treatment algorithm


fasting plasma glucose ≥7 mmol/L (or 6 to 6.9 mmol/L if large fetus/polyhydramnios)

fasting plasma glucose <7 mmol/L without large fetus/polyhydramnios




Eleanor Scott, BM, BS, MD, FRCP

Professor of Medicine (Diabetes and Maternal Health)

Leeds Institute of Cardiovascular and Metabolic Medicine

Leeds Centre for Diabetes and Endocrinology




ES has received honoraria from Abbott Diabetes Care and Lilly Diabetes for giving talks, workshops, and advisory panels. ES has received research grant funding from MRC, NIHR, and Diabetes UK.

Rebecca Spencer, MBChB, BSc, MRCOG, PhD

NIHR Clinical Lecturer in Obstetrics and Gynaecology

University of Leeds




None disclosed.


Dr Scott and Dr Spencer would like to gratefully acknowledge Dr Ellen W. Seely, Dr Chloe Zera, Dr Jeremy Soule and Dr Leonard E. Egede, previous contributors to this topic.


EWS and CZ declare that they have no competing interests. JS has undertaken research support and speakers' bureau activity for Novartis, Bristol Myers Squibb, Astra Zeneca, and Sanofi-Aventis. LEE is an author of a number of references cited in this topic.

Peer reviewers

Helen Murphy, MBBch, BAO, FRACP, MD

Clinical Professor in Medicine (Diabetes and Antenatal Care)

University of East Anglia




HM sits on the Medtronic (insulin pump and CGM manufacturer) European scientific advisory board. HM has received research support (CGM sensors and insulin pumps) at reduced cost from Medtronic, Dexcom, and Johnson & Johnson. MH has contributed to educational events sponsored by NovoNordisk, Medtronic, Dexcom, and Abbott Diabetes Care.

  • Differentials

    • Type 1 diabetes
    • Type 2 diabetes
    More Differentials
  • Guidelines

    • Standards of medical care in diabetes - 2022
    • Diabetes in pregnancy: management from preconception to the postnatal period
    More Guidelines
  • Patient leaflets

    Diabetes that develops in pregnancy (gestational diabetes)

    Diabetes: what can I do to keep healthy?

    More Patient leaflets
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