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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- T2DM = insulin resistance plus beta-cell failure; diagnosis by A1c >=6.5%, fasting glucose >=126, 2-hour OGTT >=200, or random glucose >=200 with symptoms
- Initial management: lifestyle, weight loss, cardiovascular risk reduction, and metformin unless contraindicated
- Use GLP-1 RA or dual GIP/GLP-1 RA for weight loss/ASCVD benefit; use SGLT2 inhibitor for heart failure or CKD benefit independent of A1c
- Most nonpregnant adults target A1c <7%; individualize to <6.5% if low hypoglycemia risk or <8% if frail/comorbid
- Screen complications: annual UACR/eGFR, dilated eye exam, foot exam, lipids, BP, and vaccination
Overview
Type 2 diabetes mellitus is a chronic metabolic disease caused by insulin resistance and progressive pancreatic beta-cell failure. Hyperglycemia drives microvascular injury (retinopathy, nephropathy, neuropathy) and accelerates atherosclerotic cardiovascular disease. The ADA Standards of Care emphasize individualized glycemic targets, early treatment of cardiovascular and renal risk, and medication selection based on comorbid ASCVD, heart failure, chronic kidney disease, obesity, hypoglycemia risk, and cost rather than glucose lowering alone.
Epidemiology
T2DM accounts for approximately 90-95% of diabetes in the United States. Prevalence rises with age, obesity, sedentary behavior, family history, prior gestational diabetes, polycystic ovary syndrome, and high-risk ancestry including Black, Hispanic/Latino, Native American, Asian American, and Pacific Islander populations. Cardiovascular disease is the leading cause of death in T2DM; albuminuria and declining eGFR predict both renal failure and cardiovascular events.
Clinical Features
Symptoms
Polyuria, polydipsia, nocturia, and blurred vision from osmotic diuresis and hyperosmolarity
Fatigue, recurrent vulvovaginal candidiasis, balanitis, or skin infections
Unintentional weight loss suggests marked insulin deficiency or alternative diagnosis
Peripheral neuropathy: burning, numbness, tingling, worse at night
Chest pain, dyspnea, or claudication may be the presenting macrovascular complication
Altered mental status and profound dehydration suggest HHS
Signs
Central adiposity, acanthosis nigricans, skin tags, hypertension
Reduced monofilament sensation or vibration sense in a stocking distribution
Foot ulcer, cellulitis, osteomyelitis, or Charcot arthropathy
Retinal microaneurysms, hemorrhages, cotton-wool spots, neovascularization
Orthostatic hypotension or resting tachycardia from autonomic neuropathy
Investigations
First-line
HbA1cDiagnostic if >=6.5% using standardized assay. Reflects ~3 months of glycemia; unreliable with hemolysis, recent transfusion, advanced CKD, pregnancy, or hemoglobinopathy
Fasting plasma glucoseDiabetes if >=126 mg/dL after at least 8 hours fasting; impaired fasting glucose 100-125 mg/dL
Random plasma glucoseDiabetes if >=200 mg/dL with classic symptoms or hyperglycemic crisis
Baseline cardiometabolic labsBMP/eGFR, urine albumin-to-creatinine ratio, lipid panel, ALT/AST, B12 if metformin use is planned long term
Second-line
2-hour 75 g OGTTDiabetes if >=200 mg/dL; useful when A1c/fasting glucose discordant and for gestational/postpartum assessment
Autoantibodies and C-peptideIf lean adult, ketosis, rapid insulin requirement, or diagnostic uncertainty; GAD65, IA-2, ZnT8 antibodies suggest autoimmune diabetes
Dilated retinal exam and foot examRetinopathy screening at diagnosis for T2DM; comprehensive foot exam at least annually and more often if high risk
Specialist
Continuous glucose monitoringUseful for insulin-treated T2DM, recurrent hypoglycemia, or therapy adjustment; time-in-range goal often >70% for many adults
Cardiac/renal risk stratificationASCVD risk estimation, albuminuria trend, and CKD staging guide statin, ACEi/ARB, SGLT2 inhibitor, and GLP-1 RA selection
1
Lifestyle and risk-factor treatment
- Medical nutrition therapy: reduce refined carbohydrates, sugar-sweetened beverages, and excess calories; Mediterranean/DASH-style patterns are reasonable
- Weight loss target at least 5%; 10-15% produces larger glycemic and cardiometabolic benefit
- Exercise: >=150 min/week moderate aerobic activity plus resistance training 2-3 days/week
- Smoking cessation, sleep optimization, treatment of OSA if suspected
- BP target usually <130/80 if safely achieved; high-intensity statin for most age 40-75 with diabetes and ASCVD risk factors
2
Initial pharmacotherapy
- Metformin first-line for many patients: start 500 mg daily/BID and titrate; avoid if eGFR <30, reduce/assess if eGFR 30-45
- If ASCVD or high ASCVD risk: GLP-1 RA with CV benefit (semaglutide, liraglutide, dulaglutide) or SGLT2 inhibitor with CV benefit
- If heart failure or CKD: SGLT2 inhibitor with proven benefit (empagliflozin, dapagliflozin, canagliflozin) independent of baseline A1c when eGFR allows
- If obesity predominant: semaglutide or tirzepatide can address glycemia and weight; avoid therapeutic inertia
3
Escalation and insulin
- Dual or triple therapy if A1c remains above target after ~3 months or initial A1c is markedly elevated
- Consider insulin if catabolic symptoms, weight loss, ketosis, symptomatic hyperglycemia, or A1c >10% / glucose >=300 mg/dL
- Basal insulin starting dose often 10 units nightly or 0.1-0.2 units/kg/day; titrate to fasting glucose
- Avoid sulfonylureas in high hypoglycemia risk; avoid thiazolidinediones in heart failure
4
Complication prevention
- Annual UACR and eGFR; ACEi/ARB for hypertension with albuminuria
- Retinal exam at diagnosis and at least every 1-2 years depending on findings
- Annual monofilament/pulse foot exam; daily self-inspection for neuropathy or PAD
- Vaccines: influenza, COVID-19, pneumococcal, hepatitis B if unvaccinated and age-appropriate
Complications
- Microvascular: Diabetic retinopathy, nephropathy, distal symmetric polyneuropathy, autonomic neuropathy
- Macrovascular: CAD, stroke, PAD — leading driver of mortality
- Acute metabolic: HHS, DKA in insulin-deficient or SGLT2 inhibitor-associated states, hypoglycemia from insulin/sulfonylureas
- Foot disease: Ulceration, infection, osteomyelitis, Charcot arthropathy, amputation
- Infections: Candidiasis, cellulitis, necrotizing soft tissue infections, malignant otitis externa
USMLE Step 2 CK Exam Tips
- 1Diagnosis requires confirmatory repeat testing unless classic symptoms + random glucose >=200 or hyperglycemic crisis
- 2T2DM at diagnosis already needs retinopathy screening; T1DM retinopathy screening starts 5 years after diagnosis
- 3Albuminuria + diabetes + hypertension = ACEi or ARB; do not combine ACEi + ARB
- 4Heart failure or CKD in diabetes: choose SGLT2 inhibitor even if A1c is near goal
- 5ASCVD in diabetes: choose GLP-1 RA or SGLT2 inhibitor with proven CV benefit
- 6Insulin is the next best step for catabolic symptoms, ketosis, A1c >10%, or glucose >=300
- 7Metformin can cause B12 deficiency and lactic acidosis risk in severe renal failure
practicetest your knowledge on type 2 diabetes mellitusApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — endocrine and beyond.
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