Treatment Regimen for Type 1 Diabetes Mellitus (T1DM)

1. Insulin Therapy - The Cornerstone

Insulin Preparations

A. Multiple Daily Injections (MDI) - Basal-Bolus Regimen

• Total daily dose (TDD): 0.3 to 1.0 unit/kg/day
• Basal insulin: ~50% of TDD given as long-acting analogue (glargine, detemir, or degludec) once or twice daily
• Prandial bolus: Remaining ~50% divided as rapid-acting analogue before each meal
• Dosing rule: 1 unit per 10-15 g of carbohydrate consumed + a correction factor of 1 unit to lower plasma glucose by 20-50 mg/dL above target
• Regular insulin: inject 30 minutes before meals; rapid-acting analogues: inject 15 minutes before or 15-20 minutes after starting a meal

B. Standard (Twice-Daily) Regimen

• Twice-daily injections combining NPH with regular or rapid-acting insulin
• Less flexible but reduces injection frequency
• Less likely to achieve target HbA1c compared to MDI

C. Inhaled Insulin

• Available for rapid-acting prandial use (Afrezza)
• Onset even faster than subcutaneous rapid-acting analogues (peak within 10-20 minutes)
• Rarely recommended; reserved for specialized centers

2. Continuous Subcutaneous Insulin Infusion (CSII) - Insulin Pump

• HbA1c reduction: 0.3-0.5% vs MDI
• Advantages: Reduces severe hypoglycemia, allows programmable variable basal rates (including adjustment for the "dawn phenomenon"), allows bolus dosing based on carbohydrate content + glucose corrections, more flexible lifestyle
• Infusion sites: Abdomen, flanks, upper legs, arms
• Tubeless systems available for greater convenience
• Patients must be able to revert quickly to MDI injections in case of pump failure (DKA can develop within hours given the short half-life of insulin ~5-10 minutes and no long-acting depot)

3. Sensor-Augmented Pump and Continuous Glucose Monitoring (CGM)

• CGM devices measure interstitial glucose continuously, providing real-time trends
• Sensor-augmented pumps (CGM + CSII) improve HbA1c by -0.4 to -0.6% vs standard MDI, and reduce hypoglycemia risk
• Features include automatic insulin suspension when low glucose predicted, alarms for out-of-range values

4. Closed-Loop / Automated Insulin Delivery (AID) - "Artificial Pancreas"

• Integrates real-time CGM + insulin pump + control algorithm
• Automatically adjusts insulin delivery every 5-10 minutes
• Can deliver automatic corrective boluses when glucose reaches a predetermined high threshold
• Reduces nighttime hypoglycemia, lowers HbA1c, reduces time-in-hypoglycemia
• Open-source systems (e.g., "Do-It-Yourself" loops) are also available
• Requires expert supervision and patient education

5. Glycemic Targets

• Intensive therapy (3+ injections/day + frequent monitoring) achieves better HbA1c but carries higher risk of hypoglycemia, coma, and seizures compared to standard therapy
• Intensive therapy is not recommended for patients with long-standing disease, severe microvascular complications, advanced age, or hypoglycemia unawareness
• HbA1c ≥7.5% OR <5.6% both associate with increased all-cause mortality

6. Blood Glucose Monitoring

• SMBG (self-monitoring): Several times daily before meals and at bedtime using portable meters
• CGM: Preferred over SMBG where accessible; provides continuous interstitial glucose readings
• Ketone monitoring: Test urine or capillary blood ketones when glucose is unexpectedly and persistently elevated; moderate/large ketones (≥2+ or >1.5 mmol/L) = seek urgent care for possible DKA
• Mobile apps and software assist with insulin dose calculations

7. Adjunctive (Non-Insulin) Therapies

Pramlintide (Amylin Analogue)

• Synthetic amylin given subcutaneously immediately before meals
• Delays gastric emptying, reduces postprandial glucagon, improves satiety
• Modestly lowers HbA1c by 0.3-0.5%; facilitates weight loss
• Starting dose: 15 mcg before meals, titrated to maintenance 120 mcg
• When initiating, reduce mealtime insulin dose by 50% to avoid severe hypoglycemia
• Adverse effects: nausea, anorexia, vomiting
• Contraindicated in gastroparesis, hypoglycemia unawareness
• Must not be mixed in the same syringe as insulin

SGLT2 Inhibitors (off-label / approved in some countries)

• Dapagliflozin (low dose) and sotagliflozin (SGLT1/2 dual inhibitor)
• Lower HbA1c by 0.28-0.48%; facilitate weight loss through glycosuria
• Risk: Precipitate euglycemic DKA in 3-6% of T1DM patients
• Also increase risk of urinary tract and genital yeast infections
• Approved for T1DM in parts of Europe but not approved in the US or UK for T1DM

8. Diet and Lifestyle

• Carbohydrate counting is the preferred dietary approach - insulin dose matched to carbohydrate content of each meal (ratio may vary by time of day)
• Alternatively: meal-to-meal carbohydrate consistency with fixed premeal dosing
• Avoid rapidly absorbed carbohydrates ideally; caloric restriction only if overweight/obese
• Mediterranean diet recommended (heart-healthy, as for general population)
• Individualize based on food preferences, culture, finances, physical activity, glycemic targets
• Exercise: Adjust insulin and carbohydrate intake around physical activity; temporary basal rate reductions can be used in pump users during exercise

9. Management of Acute Complications

Hypoglycemia

• Treat with 15-20g of fast-acting carbohydrates (rule of 15)
• Glucagon (IM/SC/intranasal) for severe/unconscious patients
• Prevent by careful glucose monitoring, dose adjustments, patient education

Diabetic Ketoacidosis (DKA)

• Requires urgent IV fluid resuscitation, continuous IV insulin infusion, potassium replacement
• ADA 2025 guidelines include new treatment pathways for DKA (and HHS) with outlined transition to subcutaneous insulin
• Insulin pump use can continue in hospital when clinically appropriate (per 2025 ADA update)

10. Cardiovascular and Complication Monitoring/Prevention

11. Disease-Modifying and Preventive Therapy

• Teplizumab (anti-CD3 monoclonal antibody): Approved for use in individuals at high risk for T1DM (≥2 positive autoantibodies + impaired glucose tolerance = Stage 2); a single 14-day course may delay progression to clinical T1DM by ~2 years in high-risk relatives
• Immunosuppressive agents (rituximab, cyclosporine, anti-CD3) slow early disease but effects are not sustained after withdrawal

12. Surgical / Experimental Options

• Whole pancreas transplantation: 5-year graft survival ~70%; reserved for patients already undergoing kidney transplant or those with severe metabolic instability/hypoglycemia unawareness unresponsive to conventional therapy; requires lifelong immunosuppression
• Islet cell transplantation: Experimental; limited availability; also requires immunosuppression
• Stem cell therapy: Active research area; not yet in routine use

Summary of Key Principles

1. Insulin is mandatory - no alternative replaces it in T1DM
2. Basal-bolus MDI or CSII are the preferred delivery strategies; closed-loop/AID systems represent the current gold standard when accessible
3. CGM is preferred over SMBG for glucose monitoring
4. HbA1c target ≤7% for most patients; individualize for special populations
5. Carbohydrate counting with dose adjustment is the dietary cornerstone
6. Multidisciplinary team (endocrinologist, diabetes educator, dietitian, ophthalmologist, nephrologist, podiatrist) is essential for long-term care
7. Teplizumab is a recent disease-modifying option for high-risk pre-clinical T1DM