Diabetes Management: Key Principles and Insulin Management
Symptoms and Pathophysiology
Classic symptoms of diabetes include increased thirst, frequent urination, headaches, blurred vision, and fatigue, which indicate uncontrolled hyperglycemia. 1
- Type 1 diabetes results from autoimmune destruction of pancreatic beta cells, requiring exogenous insulin from diagnosis 2
- Type 2 diabetes involves insulin resistance and progressive beta-cell dysfunction, with 90-95% of adult diabetes cases being type 2 3
- Youth with type 2 diabetes typically present with obesity (BMI ≥95th percentile), strong family history, and substantial residual insulin secretion 4
Investigations and Monitoring
HbA1c should be monitored every 3 months, with treatment intensification if goals are not met. 4
- Fasting plasma glucose (FPG) targets: 80-130 mg/dL (4.4-7.2 mmol/L) 5
- HbA1c targets: <7% for most adults with type 2 diabetes; <6.5% for youth with type 2 diabetes due to lower hypoglycemia risk 4
- Self-monitoring of blood glucose (SMBG) is required when taking insulin, initiating/changing treatment, not meeting goals, or during intercurrent illness 4
- Daily fasting glucose monitoring is essential during insulin titration 5
Lifestyle Management
An individualized medical nutrition therapy program provided by a registered dietitian is recommended for all patients with diabetes. 4
Nutrition Therapy
- Emphasize nutrient-dense foods with appropriate portions, focusing on vegetables, fruits, legumes, whole grains, and dairy products with higher fiber and lower glycemic load 4
- Weight loss ≥5% through calorie reduction and lifestyle modification benefits overweight/obese adults with type 2 diabetes 4
- Carbohydrate counting is essential for patients on flexible insulin therapy to determine mealtime insulin dosing 4
- Avoid sugar-sweetened beverages and minimize foods with added sugars 4
Physical Activity
- 60 minutes daily of moderate-to-vigorous exercise for children and adolescents 4
- Limit nonacademic screen time to <2 hours daily 4
- Include aerobic, muscle-strengthening, and bone-strengthening activities 4
Alcohol
- Maximum one drink per day for adult women, two drinks per day for adult men 4
- Chronic alcohol intake (45 g/day) causes deterioration in glucose metabolism 4
Initial Treatment Approach
Type 2 Diabetes in Adults
For adults with type 2 diabetes and HbA1c ≥9% or blood glucose ≥300-350 mg/dL with symptomatic/catabolic features, start basal-bolus insulin immediately at 0.3-0.4 units/kg/day. 5, 1
- For HbA1c <9% without ketosis: Start metformin (titrate to 2000 mg/day) plus lifestyle modification 4
- For HbA1c ≥9% without acidosis: Start metformin plus basal insulin at 0.5 units/kg/day 4
- Metformin should be continued when adding insulin unless contraindicated, as it reduces weight gain, lowers insulin requirements, and decreases hypoglycemia risk 5, 2
Type 2 Diabetes in Youth
For youth with new-onset diabetes, obesity, and clinical suspicion of type 2 diabetes, the treatment algorithm depends on HbA1c and presence of acidosis. 4
- HbA1c <8.5% without acidosis: Metformin plus lifestyle modification 4
- HbA1c >8.5% without acidosis: Metformin plus long-acting insulin at 0.5 units/kg/day, titrated every 2-3 days based on blood glucose monitoring 4
- Acidosis/DKA/HHS: Manage as type 1 diabetes with intravenous insulin until acidosis resolves, then subcutaneous insulin 4
- Check pancreatic autoantibodies; if positive, transition to type 1 diabetes management 4
Type 1 Diabetes
All patients with type 1 diabetes require multiple daily injections or insulin pump therapy from diagnosis, with total daily insulin of 0.4-1.0 units/kg/day (typically 0.5 units/kg/day for metabolically stable patients). 5, 2
- Approximately 50% as basal insulin and 50% as prandial insulin 5
- Higher doses required immediately following ketoacidosis presentation 5
Insulin Initiation: Critical Points
When to Start Insulin
Insulin must be initiated immediately for patients with ketosis/DKA, random glucose ≥250 mg/dL, or HbA1c >9%. 4
Additional indications for insulin in type 2 diabetes: 5, 2
- HbA1c ≥7.5% despite optimal oral medications
- Blood glucose ≥300-350 mg/dL with symptomatic features
- Acute illness, surgery, or pregnancy
- Contraindications to or failure of oral medications
Starting Doses
For insulin-naive type 2 diabetes patients, start with 10 units once daily or 0.1-0.2 units/kg/day of basal insulin. 5, 6
- For severe hyperglycemia (HbA1c ≥9%, glucose >300 mg/dL): Start basal-bolus regimen at 0.3-0.4 units/kg/day total, divided approximately 50% basal and 50% prandial 5, 1
- Example for 86 kg patient with severe hyperglycemia: 13 units basal insulin (glargine) once daily at bedtime plus 4 units rapid-acting insulin before each meal 1
- For hospitalized patients: 0.3-0.5 units/kg/day total daily dose, with half as basal insulin 5
- High-risk patients (elderly >65 years, renal failure, poor oral intake): Use lower doses of 0.1-0.25 units/kg/day 5
Insulin Selection
Long-acting basal insulin analogues (glargine or detemir) are preferred for basal coverage, with rapid-acting analogues (lispro, aspart, glulisine) for prandial coverage. 5, 1
- Analogue insulins are as effective as human insulin but associated with less postprandial hyperglycemia and delayed hypoglycemia 2
- Glargine should not be diluted or mixed with other insulins due to low pH 5, 6
Insulin Titration: Critical Points
Basal Insulin Titration Algorithm
Increase basal insulin by 2-4 units (or 10-15%) every 3 days until fasting blood glucose reaches 80-130 mg/dL without hypoglycemia. 5
Specific adjustments based on fasting glucose: 5
- FPG ≥180 mg/dL: Increase by 4 units every 3 days
- FPG 140-179 mg/dL: Increase by 2 units every 3 days
- FPG <80 mg/dL (>2 readings/week): Decrease by 2 units 5
Most patients can self-titrate by adding 1-2 units (or 5-10% for higher doses) once or twice weekly if fasting glucose remains above target. 5
When to Add Prandial Insulin
When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day without achieving HbA1c goals despite controlled fasting glucose, add prandial insulin rather than continuing to escalate basal insulin. 5
Signs of "overbasalization" requiring prandial insulin addition: 5
- Basal dose >0.5 units/kg/day
- Bedtime-to-morning glucose differential ≥50 mg/dL
- Hypoglycemia episodes
- High glucose variability
- Fasting glucose at target but HbA1c remains elevated after 3-6 months
Prandial Insulin Initiation
Start with 4 units of rapid-acting insulin before the largest meal or the meal causing greatest postprandial glucose excursion, or use 10% of current basal dose. 5
- Titrate by 1-2 units or 10-15% every 3 days based on pre-meal and 2-hour postprandial glucose readings 5
- Add to additional meals sequentially based on glucose patterns 5
Insulin Adjustment and Monitoring
Hypoglycemia Management
If hypoglycemia occurs, determine the cause and reduce insulin dose by 10-20% immediately. 5
- Treat with 10-20 grams of oral glucose, which raises blood glucose by 40-60 mg/dL over 30-45 minutes 4
- Increase monitoring frequency with changes in insulin dosage, concomitant drugs, meal patterns, physical activity, or in patients with renal/hepatic impairment 6
- Signs of hypoglycemia may be reduced with beta-blockers, clonidine, guanethidine, and reserpine 6, 7
Monitoring Requirements
Daily fasting blood glucose monitoring is essential during titration, with reassessments every 3 days during active titration and every 3-6 months once stable. 5
- Monitor HbA1c every 3 months 4
- Assess adequacy of insulin dose at every visit, looking for signs of overbasalization 5
- For patients on prandial insulin, monitor both fasting and postprandial glucose 5
Combination Therapy
Continue metformin when initiating or intensifying insulin therapy unless contraindicated, as it reduces weight gain, lowers insulin requirements, and decreases hypoglycemia risk. 5, 1, 2
- Consider adding GLP-1 receptor agonist to basal insulin to improve HbA1c while minimizing weight gain and hypoglycemia risk 5
- Discontinue sulfonylureas when starting multiple daily insulin injections to reduce hypoglycemia risk 1
- Do not abruptly discontinue oral medications when starting insulin due to risk of rebound hyperglycemia 2
Administration Technique
Use the shortest needles (4-mm pen or 6-mm syringe needles) as first-line choice in all patients, as they are safe, effective, and less painful. 2
- Administer subcutaneously into abdominal area, thigh, or deltoid at the same time each day 6
- Rotate injection sites within given areas to reduce risk of lipodystrophy and localized cutaneous amyloidosis 6, 2
- Avoid intramuscular injections, especially with long-acting insulins, as severe hypoglycemia may result 2
- Do not inject into lipohypertrophic lesions, as this distorts insulin absorption 2
Follow-Up Schedule
Schedule follow-up within 2-4 weeks after insulin initiation to assess initial response, adherence, and side effects. 1
- Reassess every 3 days during active titration 5
- Once stable, follow-up every 3-6 months with HbA1c monitoring 5
- More frequent monitoring required with treatment changes, intercurrent illness, or failure to meet goals 4
Critical Pitfalls to Avoid
Never delay insulin initiation in patients with severe hyperglycemia (glucose >300 mg/dL, HbA1c >10%), as oral agents alone will not achieve control. 1
- Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to overbasalization with suboptimal control and increased hypoglycemia risk 5
- Do not start with basal insulin only in patients with severe hyperglycemia (glucose >300 mg/dL, HbA1c >10%), as both basal and prandial coverage are required from the outset 1
- Do not wait longer than 3 days between basal insulin adjustments in stable patients, as this unnecessarily prolongs time to achieve glycemic targets 5
- Do not ignore the need for prandial insulin when signs of overbasalization are present 5
- Do not discontinue metformin when adding insulin unless contraindicated 5, 1
- Do not rely solely on correction (sliding scale) insulin without scheduled basal and prandial components 5
- Accidental mix-ups between insulin products can occur; instruct patients to check insulin labels before injection 6
Special Populations
Youth with Type 2 Diabetes
- If initially treated with insulin and metformin and meeting glucose goals, insulin can be tapered over 2-6 weeks by decreasing dose 10-30% every few days 4
- Consider adding GLP-1 receptor agonist or SGLT2 inhibitor approved for youth if HbA1c goals not met on metformin 4
- Prioritize and maximize non-insulin medications to minimize weight gain before escalating insulin doses 4
Renal or Hepatic Impairment
- Insulin requirements may need adjustment in patients with renal or hepatic impairment 6, 7
- Use lower starting doses (0.1-0.25 units/kg/day) for high-risk patients 5