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Type 2 diabetes mellitus in adults

Last reviewed: 6 Jun 2025
Last updated: 03 Jul 2025

Summary

Definition

History and exam

Key diagnostic factors

  • asymptomatic
  • polydipsia
  • polyuria
  • unintentional weight loss
  • polyphagia
  • hyperglycemic crisis
Full details

Other diagnostic factors

  • fatigue
  • blurred vision
  • nocturia
  • candidal infections
  • skin infections
  • urinary tract infections
  • paresthesias
  • acanthosis nigricans
Full details

Risk factors

  • older age
  • overweight/obesity
  • gestational diabetes
  • prediabetes
  • first-degree relative with type 2 diabetes
  • African, Latino, Asian or American-Indian ancestry
  • physical inactivity
  • polycystic ovary syndrome (PCOS)
  • hypertension
  • dyslipidemia
  • cardiovascular disease
  • stress
  • smoking
  • suboptimal sleep
  • low levels of testosterone/hypogonadism in men
  • mental illness
Full details

Diagnostic tests

1st tests to order

  • HbA1c
  • fasting plasma glucose
  • 2-hour plasma glucose
  • random plasma glucose
Full details

Tests to consider

  • urine ketones
  • random C-peptide
  • autoantibodies
  • urinary albumin to creatinine ratio (ACR)
  • serum creatinine and estimated GFR (eGFR)
  • fasting lipid profile
  • ECG
  • B-type natriuretic peptide (BNP)/N-terminal prohormone B-natriuretic peptide (NT-proBNP)
  • ankle-brachial index (ABI)
  • toe-brachial index (TBI)
  • dilated retinal examination
  • liver function test (LFT)
  • platelet count
  • noninvasive tests of liver elasticity
Full details

Treatment algorithm

INITIAL

at initial diagnosis

ACUTE

marked hyperglycemia nonpregnant: serum glucose ≥300 mg/dL (≥16.7 mmol/L) or hemoglobin A1c (HbA1c) >10% (>86 mmol/mol) or symptomatic

without marked hyperglycemia nonpregnant asymptomatic: serum glucose <300 mg/dL (<16.7 mmol/L) or hemoglobin A1c (HbA1c) <10% (<86 mmol/mol)

pregnant

Contributors

Authors

Klara R. Klein, MD, PhD

Assistant Professor

Director

Endocrine Diabetes and Obesity Clinical Research Unit (EnDO CRU)

Division of Endocrinology and Metabolism, Department of Medicine

University of North Carolina

Chapel Hill

NC

Disclosures

KRK is supported by the University of North Carolina Department of Medicine and School of Medicine Physician Scientist Training Program and the National Center for Advancing Translational Sciences, National Institutes of Health, through grant K12TR004416. KRK has received personal compensation for consultation from Novo Nordisk and Roche Pharmaceuticals. Additionally, KRK has received research related contracts (paid to the institution) from NCATS, Bayer, Boehringer-Ingelheim, Carmot, Diasome, Eli Lilly, Novo Nordisk, Rhythm Pharmaceuticals, and vTv Therapeutics.

Brooke C. Matson, MD, PhD

Fellow

Division of Endocrinology and Metabolism, Department of Medicine

University of North Carolina

Chapel Hill

NC

Disclosures

BCM has received research grant funding from the Endocrine Fellows Foundation. BCM has received travel support from the American Diabetes Association and the Endocrine Society to attend their annual meetings (2023 and 2024, respectively) and from Diabetes Dialog, hosted by the Barbara Davis Center for Diabetes at the University of Colorado, to attend their fellow curriculum (2023).

Acknowledgements

Dr Klara R. Klein and Dr Brooke C. Matson would like to gratefully acknowledge Dr Gregg Simonson, Dr Anders Carlson, Dr Thomas Martens, Dr Richard Bergenstal, Dr Patrick J. O'Connor, and Dr JoAnn M. Sperl-Hillen, previous contributors to this topic.

Disclosures

GS declares that his employer, HealthPartners Institute dba International Diabetes Center, has organizational interests that include receiving unrestricted educational grants from Abbott Diabetes Care and Sanofi. GS receives no personal income from any of these activities. AC is employed by HealthPartners Institute and Fabric. HealthPartners Institute has received payments on AC's behalf for research and/or consulting services from Abbott Diabetes, Dexcom, Eli Lilly, Novo Nordisk, Sanofi, Medtronic, Insulet, Tandem Diabetes, Mannkind, and United Health Group. All research or consulting fees are paid directly to HealthPartners Institute. AC receives no personal income from any of these services. AC is an author of a number of references cited in this topic. HealthPartners Institute employs TM and has contracts with Abbott Diabetes Care, Dexcom, Insulet, Eli Lilly, Medtronic, Novo Nordisk, Sanofi US Services, Inc., and Tandem for his services as a research investigator, speaker, and/or consultant. No personal income from any of these services goes to TM. TM is an author of a number of references cited in this topic. RB has received research support, has acted as a consultant, or has been on the scientific advisory board for Abbott Diabetes Care, Ascensia, Bigfoot Biomedical, Inc., CeQur, DexCom, Eli Lilly, Hygieia, Insulet, Medtronic, Novo Nordisk, Onduo, Roche Diabetes Care, Tandem Diabetes Care, Sanofi, United Healthcare, Vertex Pharmaceuticals, and Zealand Pharma. RB's employer, nonprofit HealthPartners Institute, contracts for his services and he receives no personal income. RB is an author of a number of references cited in this topic. PJO receives research funding from the National Institutes of Health on multiple projects. JMS-H is an inventor on a US patent for Disease Treatment Simulation, a simulation-based technology developed without commercial support to educate health providers on chronic disease management in a virtual environment. PJO and JMS-H are authors of a number of references cited in this topic.

Peer reviewers

David K. McCulloch, MD

Medical Director

Clinical Improvement Group Health Cooperative

Seattle

WA

Disclosures

DKM declares that he has no competing interests.

Ashim K. Sinha, MBBS, MD, FRACP, FACE

Associate Professor

Director of Diabetes and Endocrinology

Cairns Base Hospital and Diabetes Centre

Queensland

Australia

Disclosures

AKS declares that he has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

American Diabetes Association. Standards of care in diabetes - 2025. Diabetes Care. 2025 Jan 1;48(suppl 1):S1-336.Full text

Cappola AR, Auchus RJ, El-Hajj Fuleihan G, et al. Hormones and aging: an Endocrine Society scientific statement. J Clin Endocrinol Metab. 2023 Jul 14;108(8):1835-74.Full text  Abstract

Davies MJ, Aroda VR, Collins BS, et al. Management of hyperglycemia in type 2 diabetes, 2022. A consensus report by the American Diabetes Association (ADA) and the European Association for the study of diabetes (EASD). Diabetes Care. 2022 Nov 1;45(11):2753-86.Full text  Abstract

US Preventive Services Task Force. Prediabetes and type 2 diabetes: screening. Aug 2021 [internet publication].Full text

Qaseem A, Obley AJ, Shamliyan T, et al. Newer pharmacologic treatments in adults with type 2 diabetes: a clinical guideline from the American College of Physicians. Ann Intern Med. 2024 May;177(5):658-66.Full text  Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.
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