Insulin types and appropriate type of insulin with dose for different patients
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Insulin Types and Clinical Dosing Guide
Figure: Plasma insulin levels over 24 hours for all major insulin types. (Lippincott Illustrated Reviews Pharmacology)
1. Classification of Insulin Types
Rapid-Acting Analogs (Prandial)
| Insulin | Brand Names | Onset | Peak | Duration |
|---|---|---|---|---|
| Insulin lispro | Humalog, Lyumjev | 5-15 min | 1-1.5 h | 3-4 h |
| Insulin aspart | Novolog, Fiasp | 5-15 min | 1-1.5 h | 3-4 h |
| Insulin glulisine | Apidra | 5-15 min | 1-1.5 h | 3-4 h |
| Inhaled insulin | Afrezza | 5-15 min | 1 h | ~3 h |
Administration: Inject 15 min before a meal, or within 15-20 min after starting a meal. Suitable for insulin pumps and IV when needed.
Short-Acting ("Regular") Insulin
| Insulin | Onset | Peak | Duration |
|---|---|---|---|
| Human Regular (U100) | 30-60 min | 2-4 h | 6-8 h |
| Regular U500 (concentrated) | 30-60 min | 2-4 h | 6-8 h |
Administration: Inject subcutaneously 30 min before a meal. Regular insulin is the preferred form for IV infusion (DKA, surgical protocols).
Intermediate-Acting (Basal)
| Insulin | Onset | Peak | Duration |
|---|---|---|---|
| NPH (Neutral Protamine Hagedorn) | 2-4 h | 6-10 h | 10-20 h |
Formed by adding zinc and protamine to regular insulin - less soluble, slower absorption. Never give IV. Used for basal fasting glucose control.
Long-Acting Analogs (Basal - Peakless)
| Insulin | Onset | Peak | Duration |
|---|---|---|---|
| Glargine U100 (Lantus, Basaglar) | 1.5-2 h | Flat/Peakless | 16-20 h |
| Glargine U300 (Toujeo) | 1.5-2 h | Flat/Peakless | 30-36 h |
| Detemir (Levemir) | 1.5-2 h | Flat/Peakless | 16-17 h |
| Degludec U100/U200 (Tresiba) | 1.5 h | Flat/Peakless | >42 h |
- Glargine cannot be mixed with short-acting insulins (acidic pH).
- Degludec's ultra-long duration allows flexible once-daily dosing.
- Detemir may require twice-daily dosing in some T1DM patients.
Premixed Combinations
Fixed combinations of rapid/short + intermediate insulin (e.g., 70/30 NPH/Regular, 75/25 NPH/Lispro). Onset <0.25-1 h, duration up to 10-16 h. Less flexible but useful where regimen simplicity is needed.
(Katzung's Basic and Clinical Pharmacology, 16th Ed., p. 1177-1178; Goldman-Cecil Medicine, Table 210-4)
2. Insulin Dosing by Patient Type
Type 1 Diabetes (T1DM) - Adults
- Total daily dose (TDD): 0.3-1.0 units/kg/day (typically 0.4-0.7 units/kg/day in a mixed population)
- Basal: 40-50% of TDD as long-acting insulin (glargine, detemir, or degludec) once daily
- Prandial boluses: Remaining 50-60% divided before each meal using rapid-acting analog (lispro, aspart, or glulisine)
- Correction dose: 1 unit lowers glucose ~20-50 mg/dL (individualized)
- Insulin-to-carbohydrate ratio: typically 1 unit per 10-15 g of carbohydrate
Standard Basal-Bolus Regimen:
Glargine once daily (evening) + rapid-acting analog before each meal (3 injections/day) = "Multiple Daily Injection" (MDI) regimen
(Goodman & Gilman's Pharmacological Basis of Therapeutics, p. 1053; Goldman-Cecil Medicine, p. 2474)
Type 2 Diabetes (T2DM) - Initiating Insulin
Step 1: Start with Basal Insulin
- Begin with 10 units at bedtime (9 PM) + continue oral agents (especially metformin)
- Titrate by +1 unit/day until fasting glucose ≤110 mg/dL (Canadian INSIGHT protocol)
- Or increase by +3 units every 3 days if fasting glucose >110 mg/dL (PREDICTIVE 303 protocol)
Obese/Insulin-Resistant Patients:
- Start at 0.4 units/kg at bedtime
- Titrate +5 units each Monday, up to max 60 units
- If >60 units needed, add prandial insulin ("basal-plus") or reduce basal 20% + add GLP-1 agonist
Step 2: Add Prandial Insulin when:
- A1C remains >7% despite optimized basal + fasting glucose <100 mg/dL
- Basal dose has exceeded 60 units/day
- Repeated nocturnal hypoglycemia on basal titration
- BeAM factor (bedtime minus AM glucose) >55 mg/dL
Step 3: Full Basal-Bolus Regimen
- Basal (glargine) + prandial rapid-acting analog at all 3 meals
- Approximately 60% of T2DM patients achieve A1C ≤7% with basal insulin + oral agents alone
(Textbook of Family Medicine 9e, p. 1581-1590)
Gestational Diabetes / Pregnancy (GDM)
- Start: When diet and exercise fail to achieve euglycemia
- Total dose: 0.7-1.0 units/kg/day in divided doses
- Morning dose (2/3 of TDD): 1/3 Regular + 2/3 NPH (before breakfast)
- Evening dose (1/3 of TDD): 1/2 Regular + 1/2 NPH (before dinner)
- Targets: Fasting <95 mg/dL; 1-hour post-meal <140 mg/dL; 2-hour post-meal <120 mg/dL
- Insulin requirements increase with advancing gestation - review weekly
Note: Long-acting analogs (glargine, detemir) are increasingly used in pregnancy but NPH remains the most studied. Oral agents are generally avoided in GDM due to limited safety data.
(Goldman-Cecil Medicine, p. 3595)
Diabetic Ketoacidosis (DKA) / Severe Hyperglycemia
- IV Regular insulin preferred: 0.1 units/kg/hour continuous infusion
- Blood glucose falls ~10% per hour
- Acidosis corrects more slowly than hyperglycemia
- When glucose reaches ~200-250 mg/dL, reduce drip and add dextrose to IV fluids
- Transition to subcutaneous: overlap IV + SC for 1-2 hours before stopping IV to avoid rebound hyperglycemia
(Goodman & Gilman's, p. 1053)
Perioperative/Hospitalized Patients
- Hold oral agents; use insulin for glycemic control
- Use basal-bolus regimen or sliding scale with regular/rapid insulin
- At ICU discharge or when eating resumes: restart usual subcutaneous regimen with 1-2 hour overlap before stopping IV insulin
- Target glucose: 140-180 mg/dL (non-ICU); 140-180 mg/dL (ICU) per most guidelines
Insulin Pump (CSII - Continuous Subcutaneous Insulin Infusion)
- Uses only rapid-acting analog (lispro, aspart, or glulisine)
- Delivers programmable basal rates throughout the day + manual meal boluses
- Achieves the most physiologic insulin profile (see Panel C in Goodman & Gilman's Fig. 51-8)
- Preferred in T1DM patients with hypoglycemia unawareness or variable schedules
3. Key Practical Notes
| Consideration | Guidance |
|---|---|
| Lipohypertrophy | Rotate injection sites to prevent accumulation; can impair absorption |
| Hypoglycemia | Major risk of insulin treatment; educate patients on recognition and treatment |
| Weight gain | All insulin therapy causes modest weight gain |
| Mixing insulins | Only NPH + Regular/rapid analog can be mixed; glargine/detemir/degludec cannot |
| Concentrated forms | U200, U300, U500 available for insulin-resistant/high-dose patients |
| Renal impairment | Insulin clearance is reduced in CKD - doses typically need reduction; monitor closely |
| Monitoring | SMBG (4x/day: fasting + after each meal) or CGM guides titration |
Sources:
- Katzung's Basic and Clinical Pharmacology, 16th Ed. - Tables 41-5, 41-6
- Goldman-Cecil Medicine International Edition - Table 210-4
- Goodman & Gilman's Pharmacological Basis of Therapeutics - Tables 51-3, 51-4
- Lippincott Illustrated Reviews: Pharmacology - Chapter 24
- Textbook of Family Medicine, 9th Ed. - Chapter 34
- Goldman-Cecil Medicine - Pregnancy and Diabetes, Chapter 221
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