Insulin dosing guidelines provide the framework for starting, titrating, and adjusting insulin safely. Starting total daily dose is approximately 0.2 to 0.5 units per kg in insulin-naive type 2 diabetes and 0.4 to 1.0 units per kg in type 1 diabetes. Split TDD as 50 percent basal and 50 percent bolus in basal-bolus regimens, or 2/3 morning and 1/3 evening for twice-daily premix. The ADA “2-by-3” protocol titrates basal insulin in 2-unit increments every 3 days until fasting glucose reaches 80 to 130 mg/dL. Adjustments are layered on for exercise, illness, pregnancy, and concentrated formulations. All dose changes should be individualized with your clinician using home glucose or CGM data.
Starting Insulin — Total Daily Dose
| Clinical Setting | Starting TDD | Notes |
|---|---|---|
| T2D, insulin-naive, A1C 7.5–10% | 10 units basal at bedtime OR 0.1–0.2 u/kg | Add to existing oral therapy |
| T2D, insulin-naive, A1C >10% | 0.3–0.5 u/kg total | Consider basal-bolus from start |
| T2D, switching from oral failure | 0.5–0.7 u/kg total, split 50/50 | Reduce sulfonylurea on initiation |
| T1D, new adult diagnosis | 0.5–1.0 u/kg total, split 50/50 | Honeymoon phase may reduce needs |
| T1D, longstanding | 0.6–1.0 u/kg total, split 50/50 | Individualized |
| Pregnancy with diabetes | 0.7 u/kg in 1st trim; doubles by 3rd | Closer monitoring |
| Elderly, frail, renal disease | 0.2–0.3 u/kg, conservative | Higher hypo risk; relax targets |
| DKA hospitalized | IV insulin 0.1 u/kg/hr | Transition to subcut after resolution |
Splitting the Dose
- Basal-bolus — 50% as basal (once or twice daily), 50% as bolus split across meals (often even thirds or weighted by carb content)
- Premix twice daily — 2/3 of TDD before breakfast, 1/3 before evening meal
- NPH-based regimens — 2/3 morning (NPH + regular), 1/3 evening (smaller NPH + regular)
- Basal-plus — start basal, then add a single bolus at the largest meal of the day
- Pump — 40 to 50% basal as variable hourly rates, 50 to 60% as boluses
Choice of regimen depends on lifestyle, eating pattern, and clinical setting. See basal-bolus insulin regimen and insulin types comparison for detailed selection guidance.
Titration — the ADA 2-by-3 Protocol
- Set a fasting morning glucose target (typically 80 to 130 mg/dL).
- Check fasting BG daily; record results.
- Every 3 days, look at the average of the last 3 mornings.
- If above target with no hypoglycemia, increase basal by 2 units.
- If any BG below 70 or symptomatic hypo, reduce basal by 10 to 20 percent and discuss with clinician.
- Continue until on-target fasting BG.
Bolus doses are titrated against 2-hour postprandial glucose using the Insulin-to-Carb Ratio and correction factor. See carb counting for insulin and insulin correction factor.
Adjustments for Exercise
| Activity | Adjustment |
|---|---|
| Light walk under 30 min | Usually none |
| Moderate exercise 30–60 min within 90 min after meal | Reduce that meal bolus by 25–50% |
| Heavy or prolonged exercise | Reduce meal bolus 50% + 15–30g carbs every 30–60 min during activity |
| Evening exercise | Reduce evening basal by 10–20% (delayed hypo can occur up to 12 hr after) |
| Resistance training | Variable; some glucose rise initially, hypo later |
| Competition or stress | BG can rise from adrenaline; may need to bolus despite “exercise” |
Sick-Day Rules
- Never stop insulin during illness — illness raises insulin needs even if you eat less
- Check BG every 2 to 4 hours
- Check ketones (urine or blood) if BG >250 mg/dL or if vomiting
- Drink calorie-free fluids if BG high; sip juice or sports drink if BG low and unable to eat
- Increase rapid analog correction doses by 10 to 20 percent if BG persistently above target
- Call your clinician for: persistent vomiting, BG >300 not responding to correction, moderate or large ketones, signs of dehydration, or inability to keep fluids down
The ADA provides a sick-day plan template; everyone on insulin should have one written out before they need it.
Adjustments for Pregnancy
| Trimester | Insulin Pattern | Target |
|---|---|---|
| First (weeks 1–13) | May decrease in early weeks due to nausea; often stable | Premeal <95; 1-h post <140 |
| Second (weeks 14–26) | Needs rise 20–50%; review every 1–2 weeks | Same; tighter A1C goal <6.5% |
| Third (weeks 27–40) | TDD often doubles; placental hormones drive resistance | Same; possible CGM use |
| Postpartum | Drops 30–50% immediately; breastfeeding lowers needs further | Resume pre-pregnancy targets |
Pregnancy insulin choices include aspart, lispro, regular, NPH, detemir; some clinicians use glargine off-label with similar outcomes. Pre-conception counseling and team-based care matter for outcomes; see also complications and related conditions.
Concentrated Insulins
- U-200 insulin lispro (Humalog U-200) — same volume, twice the concentration; useful for high-dose patients
- U-200 insulin degludec (Tresiba U-200) — for patients with TDD over 50 basal units
- U-300 insulin glargine (Toujeo) — flatter, longer profile than glargine U-100
- U-500 insulin regular (Humulin R U-500) — reserved for severe insulin resistance (TDD >200 units); requires dedicated U-500 syringe or pen to prevent dosing errors
Always prescribe in units rather than volume to avoid catastrophic errors. The U-500 pen tracks units automatically; a TB syringe must be used if vials are dispensed.
Insulin Adjustments in Renal Disease
- Insulin clearance falls as eGFR drops below 60
- Typical reduction — 25 percent at eGFR 10 to 50; 50 percent at eGFR <10
- Avoid sulfonylureas and meglitinides; insulin and DPP-4 inhibitors are typically safer alternatives
- Hypoglycemia risk rises with renal failure; relax targets and use CGM
Hypoglycemia Response — Rule of 15
- If BG <70 with symptoms, consume 15 g fast-acting carbs (4 oz juice, 3–4 glucose tablets, 8 oz milk)
- Recheck BG in 15 minutes
- If still <70, repeat with another 15 g
- Once above 70, eat a small carb-and-protein snack if next meal is >1 hour away
- If unresponsive or unable to swallow, use glucagon (Baqsimi nasal, Gvoke autoinjector, or kit) and call 911
Practical Examples
| Patient | Starting Plan |
|---|---|
| 72 kg adult, T2D, A1C 8.5%, on metformin | 10 units glargine bedtime; titrate per 2-by-3 protocol |
| 85 kg adult, T2D, A1C 11.2%, on max orals | TDD 40 units (~0.5 u/kg): 20 basal + 7/7/6 rapid bolus with meals |
| 65 kg adult, new T1D | TDD 32 units (~0.5 u/kg honeymoon): 16 basal + 5/6/5 rapid bolus |
| 110 kg adult, severe insulin resistance, T2D, TDD 220 u | Switch to U-500 regular at 2/3 morning, 1/3 evening |
| Pregnant adult, T1D, week 28 | Increase TDD ~70% from prepregnancy; tighten targets |
External Sources
For the foundational titration evidence in type 2 diabetes, see the Treat-to-Target Trial by Riddle et al. in Diabetes Care 2003. For comprehensive contemporary guidance, see the ADA Standards of Care in Diabetes 2024.
The Bottom Line
Insulin dosing starts with a weight-based TDD (0.2 to 0.5 u/kg in insulin-naive T2D, 0.5 to 1.0 u/kg in T1D) and a planned split — 50/50 basal-bolus or 2/3 to 1/3 across two daily premix doses. Titration uses the ADA 2-by-3 protocol, increasing basal by 2 units every 3 days until on-target fasting glucose. Adjustments are layered for exercise (reduce 20 to 50 percent), illness (sick-day rules — never stop insulin), and pregnancy (often doubling TDD). Concentrated insulins require careful prescription writing. Always individualize with your prescriber using home BG or CGM data.
