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Diabetes Mellitus: Comprehensive Management

1. Overview and Goals of Management

• HbA1c: < 7.0% (individualized; < 6.5% for some; < 8% for high-risk elderly)
• Fasting blood glucose: 90-130 mg/dL
• Pre-meal glucose: 90-130 mg/dL
• Postprandial glucose: < 180 mg/dL
• Inpatient (non-critically ill): fasting < 140 mg/dL; random < 180 mg/dL

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2. Lifestyle Modification (First-Line for All Types)

Diet

• Balanced hypocaloric diet targeting 7% weight loss in overweight/obese patients
• High-fiber, low-glycemic-index foods improve glycemic control
• Reduce carbohydrate and saturated fat intake
• Avoid sugar-sweetened beverages

Exercise

• Minimum 150 minutes/week of moderate-intensity aerobic activity
• Exercise improves insulin sensitivity, glycemic control, and cardiovascular risk
• Calorie intake and medication must be balanced with activity to avoid hypoglycemia

Weight Management

• Even modest weight loss (5-10%) significantly reduces insulin resistance
• The Finnish Diabetes Prevention Study showed intensive diet and exercise reduced new diabetes in IGT patients with an NNT = 7 over 3 years, vs. NNT = 14 for metformin. - Symptom to Diagnosis, 4th Ed.

Smoking Cessation

• Smoking significantly worsens vascular complications - cessation is strongly advised

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3. Pharmacologic Management of Type 2 Diabetes

3a. Biguanides - Metformin (First-Line Agent)

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3b. Sulfonylureas (Second-Line)

• Mechanism: Bind sulfonylurea receptor on beta-cell membrane, close ATP-sensitive K+ channels, causing membrane depolarization, calcium influx, and insulin release
• Examples: Glipizide (Glucotrol) 5 mg/day, Glimepiride (Amaryl), Glyburide (DiaBeta), Gliclazide
• Best for: Early type 2 DM with fasting glucose < 300 mg/dL
• HbA1c reduction: ~1-2%
• Adverse effects: Hypoglycemia (especially in elderly, renal/hepatic impairment), weight gain
• Contraindications: Sulfa allergy, severe renal or hepatic impairment

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3c. Thiazolidinediones (TZDs)

• Examples: Pioglitazone, Rosiglitazone
• Mechanism: PPAR-gamma agonists; insulin sensitizers that decrease hepatic gluconeogenesis and increase peripheral glucose uptake
• Advantages: No hypoglycemia as monotherapy; improve lipid profile (pioglitazone)
• Adverse effects: Weight gain, fluid retention, heart failure risk, increased fracture risk; rosiglitazone associated with increased cardiac events (use with caution)

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3d. Meglitinides / Short-acting Secretagogues

• Examples: Repaglinide, Nateglinide
• Mechanism: Stimulate postprandial insulin release (must be taken with meals only)
• Advantages: Flexible dosing; useful when meals are irregular
• Adverse effects: Hypoglycemia, weight gain

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3e. Alpha-Glucosidase Inhibitors

• Examples: Acarbose, Miglitol
• Mechanism: Delay carbohydrate breakdown and absorption in the intestine, blunting postprandial glucose spikes
• Adverse effects: Diarrhea, flatulence, GI discomfort (major limiting side effect)
• HbA1c reduction: ~0.5-0.8%

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3f. DPP-4 Inhibitors (Gliptins)

• Examples: Sitagliptin (Januvia), Saxagliptin (Onglyza), Linagliptin (Tradjenta)
• Mechanism: Inhibit DPP-4 enzyme, which normally degrades GLP-1. This prolongs GLP-1 action, increasing glucose-dependent insulin secretion and suppressing glucagon
• HbA1c reduction: ~0.4-0.8%
• Advantages: Weight neutral, no hypoglycemia as monotherapy, once daily dosing; available in combination pills
• Adverse effects: Possible risk of pancreatitis; nasopharyngitis; urinary infections; saxagliptin may increase heart failure hospitalizations
• Use in CKD: Dose adjust sitagliptin/saxagliptin; linagliptin has no renal dose adjustment

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3g. GLP-1 Receptor Agonists

• Examples: Liraglutide (Victoza), Semaglutide (Ozempic, injectable; Rybelsus, oral), Exenatide, Dulaglutide, Tirzepatide (dual GIP/GLP-1)
• Mechanism: Mimic incretin GLP-1; enhance glucose-dependent insulin secretion, suppress glucagon, slow gastric emptying, reduce appetite
• Advantages: Significant weight loss, cardiovascular protection (liraglutide, semaglutide, dulaglutide proven to reduce MACE), possible renal protection
• HbA1c reduction: 0.8-2%
• Adverse effects: Nausea, vomiting, diarrhea (common especially at initiation); pancreatitis risk; contraindicated with personal/family history of medullary thyroid carcinoma or MEN2; injectable or oral forms available
• A 2025 systematic review and meta-analysis confirmed GLP-1 RAs are associated with significant GI adverse events (nausea, vomiting, diarrhea), which are dose-dependent and usually transient. (PMID: 40499738)

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3h. SGLT-2 Inhibitors

• Examples: Empagliflozin (Jardiance), Canagliflozin (Invokana), Dapagliflozin (Farxiga)
• Mechanism: Inhibit SGLT-2 in the proximal renal tubule, reducing glucose reabsorption and promoting urinary glucose excretion. Lower the glycosuria threshold from ~180 mg/dL to ~40 mg/dL
• Advantages:
  • Cardiovascular protection: Canagliflozin and empagliflozin are FDA-approved for CV risk reduction in T2DM with established CVD
  • Reduce hospitalization for heart failure
  • Reduce albuminuria and slow nephropathy progression
  • Modest weight loss and blood pressure reduction
• Adverse effects: Urinary and genital mycotic infections, hypotension, volume depletion, DKA (including euglycemic DKA), Fournier's gangrene
• Contraindications: GFR < 30-45 (reduced efficacy + safety concerns); caution in inpatient settings (safety not established)
• ROSEN's Emergency Medicine; Goldman-Cecil Medicine

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3i. Amylin Analog

• Pramlintide (Symlin): injectable, 3x/day before meals
• Decreases gastric emptying and glucagon secretion
• Approved for both Type 1 and Type 2 DM
• May promote weight loss; used as an adjunct to insulin

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Summary Table: Oral/Injectable Agents for Type 2 DM

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4. Insulin Therapy

Types of Insulin

• Start basal insulin (glargine, detemir, or NPH) at 0.1-0.2 units/kg/day (~10 units/day) with follow-up in 3-4 days for dose adjustment
• Add prandial (rapid-acting) insulin when postprandial glucose remains uncontrolled despite basal

Insulin Delivery Devices

• Syringes, insulin pens, insulin pumps (CSII)
• Insulin pumps (CSII): Provide continuous subcutaneous insulin infusion; allow patient-administered boluses; support tight glycemic control
• Continuous Glucose Monitoring (CGM): Real-time glucose readings every 5 minutes; reduces hypoglycemia risk and improves glucose control, especially in T1DM
• Bionic/closed-loop pancreas: Integrates CGM with insulin (and glucagon) delivery; improves mean glycemic levels with fewer hypoglycemic episodes

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5. Inpatient Diabetes Management

• Non-critically ill: Target fasting glucose < 140 mg/dL; random/postprandial < 180 mg/dL using scheduled subcutaneous insulin (basal ± prandial). Avoid "sliding scale" only regimens as they increase hypoglycemia risk
• Critically ill (ICU): Target glucose 140-180 mg/dL using variable-rate IV insulin infusion; intensive control (< 110 mg/dL) is harmful (increases hypoglycemic episodes and mortality)
• Type 1 DM inpatients: Usually continue home insulin regimen; extra attention to hypoglycemia from missed meals
• On discharge: Resume oral medications if eating normally and preadmission control was adequate; SGLT-2 inhibitor safety in inpatients remains uncertain
• Goldman-Cecil Medicine, International Edition

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6. Hypoglycemia - Management and Prevention

• Strict glycemic control, prolonged fasting, exercise
• Insulin/sulfonylurea use, alcohol, renal/hepatic disease
• Elderly patients (blunted adrenergic response)

• Conscious patient: 15-20 g fast-acting carbohydrates (glucose tablets, juice, regular soda)
• Unconscious/severe: IV dextrose (25-50 mL of D50W) or IM/SC glucagon 1 mg
• Recheck glucose in 15 minutes; re-treat if still < 70 mg/dL

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7. Management of Specific Complications

Diabetic Nephropathy

• Optimize glycemic and blood pressure control (target BP < 130/80 mmHg)
• First-line: ACE inhibitor or ARB (reduce proteinuria and slow progression)
• SGLT-2 inhibitors reduce albuminuria and slow CKD progression
• Avoid metformin when GFR < 30

Diabetic Retinopathy

• Annual dilated fundoscopic exam
• Tight glycemic control slows progression
• Laser photocoagulation for proliferative retinopathy; anti-VEGF injections for diabetic macular edema

Diabetic Neuropathy

• Tight glycemic control prevents/slows progression
• Pain management: duloxetine (first-line), pregabalin, gabapentin, tricyclic antidepressants
• Foot care: regular podiatry, protective footwear, daily foot inspection

Cardiovascular Disease

• Statin therapy for all diabetic patients ≥ 40 years (or younger with risk factors) - LDL target < 70 mg/dL in high-risk patients
• Aspirin therapy in established CVD
• GLP-1 RAs (liraglutide, semaglutide) and SGLT-2 inhibitors (empagliflozin, canagliflozin) have proven CV mortality benefit
• Blood pressure management: ACE inhibitor/ARB preferred

Diabetic Ketoacidosis (DKA) - mainly Type 1

• IV fluid resuscitation, IV regular insulin infusion, potassium replacement
• Identify and treat precipitating cause
• Transition to subcutaneous insulin when anion gap closes and patient is eating

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8. Special Situations

Gestational Diabetes (GDM)

• Screen at 24-28 weeks with 75g OGTT
• First-line: dietary modification and exercise
• If targets not met: insulin therapy preferred; metformin and glyburide may be used but have limitations
• Postpartum: rescreen at 6-12 weeks; 50% risk of T2DM within 10 years

Prediabetes

• Lifestyle modification (NNT = 7 over 3 years to prevent T2DM) is more effective than metformin (NNT = 14)
• Metformin can be used, especially in high-risk individuals (BMI > 35, younger age, gestational diabetes history)

Renal Impairment

• Adjust/avoid: metformin (GFR < 30), sulfonylureas, SGLT-2 inhibitors
• Safer options: insulin, DPP-4 inhibitors (dose-adjust), GLP-1 RAs (with caution)
• GFR 30-60: may continue low-dose metformin with monitoring

Pancreas Transplantation

• Combined pancreas-kidney transplant for ESRD from diabetic nephropathy
• Ameliorates nephropathy, neuropathy, retinopathy, gastroparesis

• 75% graft survival and patient survival at 1 year in specialized centers

• Complications: rejection, pancreatitis, graft thrombosis, immunosuppression risks

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9. Monitoring and Follow-Up

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10. Emerging and Technology-Based Management

• Closed-loop insulin delivery (artificial pancreas): Integrates CGM + pump, automates insulin (and glucagon) dosing; improves glycemic time-in-range with less hypoglycemia
• Tirzepatide (dual GIP/GLP-1 agonist): Newer agent with superior HbA1c and weight reduction vs. semaglutide alone
• Inhaled insulin (Afrezza): Ultra-rapid-acting; associated with cough, contraindicated in reactive airway disease
• Biosimilar insulins: Expanding access and reducing cost
• Non-invasive glucose monitoring: Fiberoptic technology in development for the future insulin pumps
• A 2025 network meta-analysis in BMJ found intermittent fasting strategies significantly improve cardiometabolic risk factors including glycemic parameters, potentially as an adjunct to medical therapy (PMID: 40533200)

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• ROSEN's Emergency Medicine: Concepts and Clinical Practice - Management of Diabetes Mellitus
• Goldman-Cecil Medicine, International Edition - Inpatient Management of Diabetes / Hypoglycemia
• Katzung's Basic and Clinical Pharmacology, 16th Edition - Medications for Type 2 Diabetes
• Symptom to Diagnosis: An Evidence-Based Guide, 4th Ed. - Treatment of Prediabetes
• Harrison's Principles of Internal Medicine, 22nd Ed. - Establishment of Target Level of Glycemic Control
• PubMed: GLP-1 RA GI adverse events meta-analysis 2025 | Intermittent fasting BMJ network meta-analysis 2025