Type 1 Diabetes Mellitus vs Type 2 Diabetes Mellitus
Type 1 Diabetes Mellitus and Type 2 Diabetes Mellitus are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Type 1 Diabetes Mellitus vs Type 2 Diabetes Mellitus at a glance
- Type 1 Diabetes Mellitus: Autoimmune destruction of pancreatic beta cells leading to absolute insulin deficiency.
- Type 2 Diabetes Mellitus: Insulin resistance with progressive beta-cell dysfunction; most common form of diabetes.
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Side-by-side comparison
| Feature | Type 1 Diabetes Mellitus | Type 2 Diabetes Mellitus |
|---|---|---|
| At a glance | Autoimmune destruction of pancreatic beta cells leading to absolute insulin deficiency. | Insulin resistance with progressive beta-cell dysfunction; most common form of diabetes. |
| Classic presentation | Lean young patient with rapid onset of polyuria, polydipsia, weight loss, sometimes presenting in DKA.; Classic triad: polyuria, polydipsia, polyphagia; Unintentional weight loss despite normal or increased intake; Fatigue, weakness, blurred vision; May present with DKA as initial manifestation (~30% of pediatric cases): nausea,… | Acanthosis nigricans on the posterior neck in an overweight adult is a classic sign of insulin resistance.; Often asymptomatic; diagnosed on screening labs; Polyuria, polydipsia, polyphagia (less prominent than T1DM); Fatigue, blurred vision, slow wound healing; Recurrent infections (yeast, UTI, skin); May present with complications:… |
| Workup / key labs | ADA criteria: A1c ≥6.5%, fasting glucose ≥126 mg/dL, 2-hr OGTT ≥200 mg/dL, or random ≥200 mg/dL with symptoms. T1DM confirmed by positive autoantibodies and/or low C-peptide.; Fasting plasma glucose ≥126 mg/dL on 2 occasions, OR random glucose ≥200 mg/dL with symptoms, OR A1c ≥6.5%, OR 2-hour OGTT ≥200 mg/dL; Islet autoantibodies (≥1… | A1c ≥6.5%, fasting glucose ≥126 mg/dL (8-hr fast), 2-hr OGTT ≥200 mg/dL (75 g load), or random ≥200 mg/dL with symptoms. Prediabetes: A1c 5.7-6.4%, fasting 100-125, OGTT 140-199.; Screening: USPSTF recommends screening adults 35-70 with overweight/obesity; ADA recommends starting at age 35 for all, earlier with risk factors; A1c ≥6.5%,… |
| Imaging | Not routinely needed for diagnosis; Dilated retinal exam at diagnosis and annually thereafter | Not routine for diagnosis; Dilated retinal exam at diagnosis and annually; Consider liver imaging if AST/ALT elevated (NAFLD evaluation) |
| First-line treatment | Lifelong exogenous insulin — basal-bolus regimen mimicking physiologic secretion; Long-acting basal insulin: glargine (Lantus, Basaglar, Toujeo), detemir, degludec (Tresiba) — once daily; Rapid-acting prandial insulin: lispro (Humalog), aspart (Novolog), glulisine (Apidra) — at meals based on carb counting; Insulin pump therapy (CSII)… | Lifestyle modification: 5-10% weight loss, Mediterranean/DASH diet, 150 min/week moderate aerobic exercise + resistance training, smoking cessation; Biguanide — metformin: first-line for most patients (unless contraindicated); start 500 mg daily, titrate to 1000 mg BID; reduces hepatic gluconeogenesis; weight neutral; low hypoglycemia… |
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