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Management of Newly Diagnosed Diabetes Mellitus - Step-by-Step Algorithm

Sources: Harrison's Principles of Internal Medicine 22E (2025), Textbook of Family Medicine 9e, ADA Standards of Care 2025

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STEP 0 - CONFIRM DIAGNOSIS & CLASSIFY TYPE

• HbA1c ≥ 6.5% (preferred first-line per ADA 2024/2025)
• Fasting plasma glucose ≥ 126 mg/dL
• 2-hour OGTT ≥ 200 mg/dL
• Random plasma glucose ≥ 200 mg/dL + symptoms

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STEP 1 - ESTABLISH THE MULTIDISCIPLINARY TEAM

• Primary care provider / endocrinologist
• Certified diabetes educator (DSMES - Diabetes Self-Management Education and Support)
• Dietitian / nutritionist
• Pharmacist
• Behavioral health professional (screen for depression, anxiety, diabetes distress)
• Relevant specialists as complications arise (ophthalmology, nephrology, cardiology, podiatry, neurology)

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STEP 2 - SET INDIVIDUALIZED GLYCEMIC TARGETS

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STEP 3 - LIFESTYLE INTERVENTION (Foundation for ALL patients)

3a. Medical Nutrition Therapy (MNT)

• Type 2 DM: Caloric reduction, increase physical activity, target 5-10% weight loss from baseline
• Very-low-carbohydrate diets can produce dramatic glucose lowering in newly diagnosed T2DM
• Emphasize plant-based proteins and fiber (ADA 2025)
• Sodium < 2,300 mg/day
• Prioritize water over sweetened beverages
• Vitamin D and calcium as recommended for bone health

3b. Physical Activity

• 150 min/week of moderate-intensity aerobic exercise, distributed over at least 3 days (no gap > 2 consecutive days)
• Add resistance training, flexibility, and balance exercises
• Reduce sedentary time throughout the day
• ADA 2025 specifically emphasizes meeting resistance training guidelines, especially for patients on weight-management pharmacotherapy

3c. Sleep

• ADA 2025 (new): Sleep is now highlighted as a central component equal to diet and exercise
• Address sleep disorders (obstructive sleep apnea is common in T2DM)

3d. Smoking, alcohol, and substance cessation

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STEP 4 - PHARMACOLOGIC MANAGEMENT

FOR TYPE 2 DM:

AT DIAGNOSIS
     │
     ▼
Is the patient SEVERELY symptomatic OR HbA1c ≥ 10-12%?
     │
    YES ──────────────────────────────────────────────────►  START INSULIN
     │                                                         (see Step 4c)
     NO
     │
     ▼
Does the patient have ESTABLISHED CVD, HEART FAILURE,
or CHRONIC KIDNEY DISEASE (CKD)?
     │
    YES ──────────────────────────────────────────────────►  STEP 4b (below)
     │
     NO
     │
     ▼
     STEP 4a - STANDARD PATHWAY

STEP 4a - Standard Pathway (No compelling comorbidities, HbA1c < 10%)

• Start low, titrate slowly (minimize GI side effects)
• Contraindications: eGFR < 30 mL/min, iodinated contrast (hold temporarily), hepatic failure, excessive alcohol
• Also offers cardiovascular and possible cancer-protective benefits
• Reassess in 3 months

Metformin → HbA1c not at goal in 3 months?
     │
     ▼
Add a second agent based on patient profile:

Still not at goal after 3 months on dual therapy?
     │
     ▼
Triple therapy or add insulin (basal insulin first)

STEP 4b - Patient with CVD / Heart Failure / CKD

• GLP-1 RA with proven CVD benefit (liraglutide, semaglutide, dulaglutide) → for ASCVD
• SGLT-2 inhibitor (empagliflozin, dapagliflozin, canagliflozin) → for heart failure or CKD (proven cardiorenal protection independent of glucose lowering)
• Can use both in combination for maximum organ protection

STEP 4c - Insulin Initiation (T2DM)

• HbA1c > 8% on oral agents despite adequate trials
• Symptomatic hyperglycemia at diagnosis (HbA1c > 10-12%)
• Pregnancy, surgery, hospitalization, or steroid use
• Beta-cell failure (secondary oral agent failure)

1. Start basal insulin (glargine or degludec preferred over NPH - less nocturnal hypoglycemia)
2. Starting dose: 10 units/night OR 0.1-0.2 units/kg/night
3. Titrate by 2 units every 3 days targeting fasting glucose 80-130 mg/dL
4. If postprandial glucose remains high: add prandial (rapid-acting) insulin before largest meal
5. Full basal-bolus regimen: basal + rapid-acting (lispro, aspart, or glulisine) before each meal

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FOR TYPE 1 DM:

DIAGNOSIS CONFIRMED
     │
     ▼
INSULIN IS MANDATORY - no oral agents replace insulin in T1DM
     │
     ▼
CHOOSE DELIVERY METHOD
     │
     ├── Automated Insulin Delivery (AID) system ← PREFERRED (ADA 2025)
     │       (Sensor-augmented pump + CGM + algorithm)
     │
     └── Multiple Daily Injections (MDI)
             │
             ├── Basal: glargine or degludec once daily
             └── Bolus: lispro / aspart / glulisine before each meal
                         (using insulin-to-carbohydrate ratio + correction dose)
     │
     ▼
TARGET: HbA1c < 7% (individualized)
CGM is strongly recommended for all T1DM patients

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STEP 5 - MONITORING

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STEP 6 - MANAGE COMORBIDITIES & COMPLICATIONS

• Hypertension: ACE inhibitor or ARB preferred (nephroprotective) - target < 130/80 mmHg in high-risk
• Dyslipidemia: Statin therapy for most adults with DM aged 40-75; high-intensity statin if CVD present
• Obesity: GLP-1 RA or tirzepatide (dual GLP-1/GIP agonist) have strongest evidence; bariatric surgery for BMI ≥ 35 with T2DM
• MASLD (metabolic-associated steatotic liver disease): ADA 2025 - consider resmetirom (thyroid hormone receptor beta agonist) for T2DM + MASLD with moderate-advanced fibrosis (specialist-managed)
• Antiplatelet therapy: Aspirin for established CVD; discuss risk/benefit for primary prevention
• Vaccinations: Influenza annually; pneumococcal; Hepatitis B series; COVID-19

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STEP 7 - PSYCHOSOCIAL SUPPORT & REASSESSMENT

• Screen at diagnosis (and repeatedly) for: diabetes distress, depression, anxiety, fear of hypoglycemia
• ADA 2025 adds screening of caregivers and family members as well
• Address social determinants of health (food access, financial barriers, cultural factors)
• Reassess DSMES annually and at every major life transition

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Quick Reference Summary

NEWLY DIAGNOSED DM
       │
       ├─ CONFIRM TYPE (T1 / T2 / Other)
       ├─ SET TARGETS (individualized HbA1c, BP, lipids)
       ├─ LIFESTYLE (MNT + exercise 150 min/wk + sleep + smoking cessation)
       ├─ PHARMACOTHERAPY
       │       ├─ T1DM → Insulin always (AID preferred)
       │       └─ T2DM → Metformin ± CVD/HF/CKD-directed agent
       │                  → Escalate every 3 months if target not met
       │                  → Add insulin when HbA1c > 8% on oral agents
       ├─ MONITOR (HbA1c, CGM, BP, lipids, renal, eyes, feet)
       ├─ TREAT COMORBIDITIES (HTN, dyslipidemia, obesity)
       └─ PSYCHOSOCIAL CARE + DSMES

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• Harrison's Principles of Internal Medicine 22E (2025) - Chapter 416: Diabetes Mellitus: Management and Therapies
• Textbook of Family Medicine 9e - Chapter 34: Medical Management of T2DM
• ADA Standards of Care in Diabetes 2025

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Diabetic Ketoacidosis (DKA) - Deep Management Guide

Sources: Harrison's Principles of Internal Medicine 22E (2025), Goldman-Cecil Medicine, Rosen's Emergency Medicine, ADA Standards of Care 2025, ADA/EASD 2024 Consensus Report on Hyperglycemic Crises

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PART 1: PATHOPHYSIOLOGY (Why Everything Happens)

INSULIN DEFICIENCY + COUNTER-REGULATORY HORMONE EXCESS
                    │
         ┌──────────┼──────────────┐
         │                        │
  LIVER: Glycogenolysis      ADIPOSE: Lipolysis
  Gluconeogenesis ↑          Free Fatty Acids ↑
         │                        │
    HYPERGLYCEMIA           Liver → Ketone bodies
         │                (β-hydroxybutyrate,
  Osmotic diuresis          acetoacetate, acetone)
         │                        │
    Dehydration              METABOLIC ACIDOSIS
    Electrolyte loss              │
         │                  Kussmaul breathing
    Hemoconcentration        (respiratory compensation)
         │
   Worsens hyperglycemia

• Sodium: 7-10 mEq/kg
• Potassium: 3-5 mEq/kg (body depleted despite often-normal serum level due to acidosis)
• Chloride: 3-5 mEq/kg
• Phosphorus: ~1-2 mEq/kg

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PART 2: PRECIPITATING CAUSES ("The 5 I's + Drugs")

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PART 3: CLINICAL FEATURES

Symptoms (develop over hours to days):

• Polydipsia, polyuria, polyphagia
• Nausea, vomiting
• Abdominal pain (~50% of cases - can mimic acute abdomen)
• Weakness, weight loss, blurred vision

Physical Signs:

• Tachycardia (dehydration)
• Hypotension / orthostatic changes (volume depletion)
• Kussmaul breathing - deep, rapid respirations (respiratory compensation for acidosis)
• Fruity / acetone breath (acetone exhalation)
• Dry skin and mucous membranes (dehydration)
• Altered mental status / coma (severe cases)
• Fever - usually from precipitating infection (DKA itself rarely causes fever)

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PART 4: INVESTIGATIONS & DIAGNOSTIC FINDINGS

Diagnostic Triad (all 3 must be present):

Full Laboratory Profile:

Severity Classification:

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PART 5: TREATMENT ALGORITHM - STEP BY STEP

PATIENT ARRIVES WITH SUSPECTED DKA
            │
            ▼
STEP 1: IMMEDIATE ASSESSMENT & STABILIZATION (First 30 minutes)
            │
            ▼
STEP 2: CONFIRM DIAGNOSIS - CHECK GLUCOSE + β-HYDROXYBUTYRATE + VBG
            │
            ▼
STEP 3: IV FLUIDS - Start immediately
            │
            ▼
STEP 4: CHECK POTASSIUM before insulin
            │
            ├── K < 3.3: Replace K+ first, HOLD insulin
            ├── K 3.3-5.0: Start K+ + insulin together
            └── K > 5.0: Start insulin, hold K+ supplementation
            │
            ▼
STEP 5: INSULIN - Start 1 hour after fluids (never before K+ checked)
            │
            ▼
STEP 6: MONITOR HOURLY - glucose, K+, response
            │
            ▼
STEP 7: When glucose < 250 mg/dL → Add DEXTROSE to IV fluids
            │
            ▼
STEP 8: IDENTIFY & TREAT PRECIPITATING CAUSE
            │
            ▼
STEP 9: TRANSITION TO SUBCUTANEOUS INSULIN when DKA resolves

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PART 6: DETAILED TREATMENT WITH EXACT DOSES

A. AIRWAY & RESUSCITATION (Immediate)

• If comatose or vomiting with altered consciousness: intubate (protect airway)
• If intubated: maintain hyperventilation to prevent worsening acidosis
• If in hypovolemic shock: aggressive fluid boluses with vasopressors as needed
• Supplemental O2 if SpO2 < 94%
• Insert Foley catheter to monitor urine output (target 0.5-1 mL/kg/hr)
• Insert NGT if vomiting or gastroparesis

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B. INTRAVENOUS FLUIDS

Phase 1 - Emergency Resuscitation (First 1-2 hours):

• 0.9% Normal Saline (isotonic crystalloid)
• Dose: 1 L over the first hour (500-1000 mL/hr)
• Can repeat until hemodynamic stability is restored
• Alternative: Balanced crystalloid (Lactated Ringer's / PlasmaLyte) - associated with more rapid DKA resolution and less hyperchloremia

• 0.9% Normal Saline: 500 mL/hr x 2-4 hours
• Note: Avoid large volumes of 0.9% NS over extended periods - causes hyperchloremic non-anion gap metabolic acidosis

Phase 2 - Correction of remaining fluid deficit (Hours 2-24):

• Switch to 0.45% saline (half normal saline) at 250-500 mL/hr
• OR continue balanced crystalloid
• Remaining 3-5L fluid deficit should be replaced over 24 hours total
• When glucose falls below 250 mg/dL: Switch to 5% Dextrose + 0.45% saline at 150-250 mL/hr (to prevent hypoglycemia while continuing insulin to clear ketones)

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C. POTASSIUM REPLACEMENT (CRITICAL - must check before insulin)

• Use KCl (potassium chloride) added to IV bags
• Maximum safe IV rate: 10-20 mEq/hr (never give undiluted IV bolus - fatal)
• Recheck serum K+ at baseline, 2 hours after insulin start, then every 4 hours
• Oral potassium supplementation can supplement IV once patient tolerating PO

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D. INSULIN THERAPY

Severe DKA - IV Regular Insulin Infusion (preferred route for sicker patients):

• Mix Regular insulin (short-acting / soluble insulin) 50 units in 500 mL 0.9% NS = 0.1 units/mL
• Flush first 50 mL through the tubing before connecting to patient (insulin adsorbs to plastic tubing)

• Start at 0.1 units/kg/hour continuous IV infusion (up to 5-10 units/hr maximum)
• Example: 70 kg patient → 7 units/hour

• Blood glucose should fall 50-75 mg/dL per hour
• Check capillary glucose every 1-2 hours

• If glucose does not fall by 50 mg/dL in first hour: double the infusion rate
• When glucose reaches 250 mg/dL: Add 5% dextrose to IV fluids AND reduce insulin to 0.02-0.05 units/kg/hr (but do NOT stop insulin - ketones still need clearing)
• Maintain glucose at 150-250 mg/dL until DKA resolves

Mild-Moderate DKA - Subcutaneous Rapid-Acting Insulin (selected patients):

• ADA 2024/2025 now endorses SC route for uncomplicated mild-moderate DKA in patients who are well-hydrated, alert, and compliant
• Use rapid-acting insulin analogue (lispro or aspart): 0.1-0.2 units/kg SC every 1-2 hours
• Avoid SC insulin if shocked (poor perfusion impairs absorption)

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E. PHOSPHATE REPLACEMENT

• Serum phosphate < 1.0 mEq/L (< 0.32 mmol/L)
• With clinical signs: muscle weakness, cardiac impairment, respiratory failure, hemolytic anemia

• Replace at 0.1-0.2 mmol/kg/hr IV over 6-12 hours (using KPO₄ rather than KCl for some of the potassium requirement)

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F. MAGNESIUM REPLACEMENT

• Worsens nausea and vomiting
• Causes refractory hypokalemia and hypocalcemia
• Can cause fatal cardiac dysrhythmias

• MgSO4 (Magnesium Sulfate): 1-3 g IV in 100 mL NS over 1-2 hours (typical adult)

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G. BICARBONATE - HIGHLY RESTRICTED USE

• Worsens hypokalemia (bicarbonate drives K+ into cells)
• Delays clearance of ketosis
• Causes paradoxical CSF acidosis (CO₂ crosses blood-brain barrier, HCO₃⁻ does not)

• Arterial pH < 7.0 (severe acidosis)
• Life-threatening hyperkalemia with ECG changes
• Hemodynamic instability that is not responding to fluids (impending cardiac arrest)

• Sodium bicarbonate 8.4% (1 mEq/mL): 50-100 mmol (50-100 mEq) in 400 mL sterile water, infuse over 2 hours with 20 mEq KCl co-administered
• Recheck pH after 2 hours; repeat if still < 7.0
• Stop when pH ≥ 7.0

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H. TREAT THE PRECIPITATING CAUSE

• Infection: Blood cultures + urine cultures → Start broad-spectrum antibiotics (e.g., piperacillin-tazobactam or ceftriaxone depending on suspected source)
• MI: ECG, troponins → Cardiology consult
• Pneumonia: Chest X-ray → Antibiotics
• Review all medications: Hold SGLT-2 inhibitors permanently until full resolution

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PART 7: MONITORING FLOW SHEET (ICU)

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PART 8: CRITERIA FOR DKA RESOLUTION

Do NOT stop insulin just because glucose falls - ketoacidosis may still be present. Keep insulin running and add dextrose instead.

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PART 9: TRANSITION TO SUBCUTANEOUS INSULIN

1. Give the first SC injection 1-2 hours BEFORE stopping the IV insulin infusion (due to the short 3-10 minute half-life of IV insulin - stopping abruptly causes rapid fall in circulating insulin)
2. If patient was on insulin prior: restart prior regimen
3. If new T1DM: start a basal-bolus regimen
   • Basal: Insulin glargine or degludec 0.2-0.3 units/kg once daily SC
   • Bolus: Rapid-acting insulin (lispro/aspart) with each meal
4. Continue basal insulin even during hospitalization if patient was on it (ADA 2024/2025)

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PART 10: COMPLICATIONS TO WATCH FOR

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PART 11: QUICK REFERENCE SUMMARY BOX

DKA MANAGEMENT AT-A-GLANCE
═══════════════════════════

FLUIDS:
• 0.9% NS 1L/hr x 1-2h (resuscitation)
• Then 0.45% NS at 250-500 mL/hr (correction)
• Add D5W/D5-0.45% NS when glucose < 250 mg/dL

POTASSIUM:
• K < 3.3 → Give 20-40 mEq/hr, HOLD insulin
• K 3.3-5.0 → Add 20-30 mEq/L to IV fluids + insulin
• K > 5.0 → Start insulin, no K supplement

INSULIN:
• IV Regular insulin: 0.1 units/kg/hr (no bolus)
• Target: glucose drop 50-75 mg/dL/hr
• When glucose < 250: add dextrose + reduce to 0.02-0.05 u/kg/hr
• DO NOT stop insulin until DKA resolved

BICARBONATE:
• ONLY if pH < 7.0: NaHCO3 50-100 mEq over 2 hours + 20 mEq KCl

RESOLUTION CRITERIA:
• Glucose < 200 + β-OHB < 0.6 mmol/L + pH > 7.3 + HCO3 ≥ 15

TRANSITION:
• Give SC basal insulin 1-2 hrs BEFORE stopping IV insulin drip

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• Harrison's Principles of Internal Medicine 22E (2025) - Chap. 416
• Rosen's Emergency Medicine (9e) - Chap. 115
• Goldman-Cecil Medicine - Chap. 210
• ADA/EASD 2024 Consensus Report on Hyperglycemic Crises in Adults (Diabetologia 2024)
• ADA Standards of Care in Diabetes 2025