Insulin Dosage Calculator
Calculate precise insulin doses for meals and corrections with step-by-step guidance.
Related Calculators
Explore other useful calculators that might help you
Ideal Weight Calculator
Find your ideal weight range based on height, age, and body frame
Body Fat Calculator
Get an accurate estimate of your body fat percentage using proven methods
Calorie Intake Calculator
Find out how many calories you need to consume daily for your goals
Insulin Dosing for Meals: Overview
Understanding how insulin works and why proper dosing is essential
Insulin is the hormone that enables the body to use glucose from food. In type 1 diabetes (T1D) the pancreas produces little or no insulin, so people must take insulin by injection or pump to process meal glucose. In type 2 diabetes (T2D), insulin resistance means higher levels of insulin are needed; many patients eventually require insulin shots in addition to pills.
Insulin cannot be taken orally (it would be broken down in digestion), so it's injected subcutaneously (often with a pen or pump). Modern insulin therapy mimics normal physiology with basal (long-acting) insulin to cover baseline needs and bolus (short- or rapid-acting) insulin to cover meals.
Types of Insulin
| Insulin Type | Onset | Peak Effect | Duration | Examples |
|---|---|---|---|---|
| Rapid-acting (bolus) | ~15 minutes | 1–2 hours | 2–4 hours | Aspart (Novolog), Lispro (Humalog), Glulisine (Apidra) |
| Regular (short-acting) | ~30 minutes | 2–3 hours | 3–6 hours | Human Regular (Humulin R) |
| Intermediate (NPH) | 2–4 hours | 4–12 hours | 12–18 hours | NPH (Humulin N, Novolin N) |
| Long-acting (basal) | 2–4 hours | No pronounced peak | ~24 hours | Glargine (Lantus, Basaglar), Detemir (Levemir) |
| Ultra long-acting | ~6 hours | No peak | 36+ hours | Degludec (Tresiba) |
Timing and Technique
Beyond what insulin to take, proper timing and technique are crucial: experts advise injecting rapid insulin before meals so it acts as food glucose rises. For example, regular insulin typically should be given ~30 minutes pre-meal. Rotating injection sites (e.g. abdomen, arm, thigh) is also important to ensure consistent absorption.
Calculating Dose with Insulin-to-Carb Ratios
The foundation of flexible meal dosing
A key tool for flexible meal dosing is the insulin-to-carbohydrate ratio (ICR). The ICR tells how many grams of carbohydrate are covered by 1 unit of rapid-acting insulin. For example, an ICR of 1:10 means 1 unit covers 10 g of carbs.
Basic Formula
Units = Total Carbs (g) ÷ ICR (g/unit)
Example: A 70g carbohydrate meal with a 1:10 ratio requires 7 units of insulin (70 ÷ 10 = 7).
Higher Insulin Sensitivity
Lower ICRs (e.g. 1:5) - 1 unit covers fewer carbs
Lower Insulin Sensitivity
Higher ICRs (e.g. 1:15) - 1 unit covers more carbs
Key Points for ICR Use:
- Count carbs (in grams) for your meal
- Apply ratio: Units = total carbs (g) ÷ ICR (g/unit)
- Adjust as needed: Rounding to half or whole units is common
- If BG was high after similar meals, a slightly lower ICR (more insulin per gram) might be needed
Correction Doses (Insulin Sensitivity)
Bringing high blood glucose down to target
A correction factor (also called the insulin sensitivity factor, ISF) is used to bring a high blood glucose down to target. It defines how much 1 unit of insulin will lower your BG (e.g. "1 unit per 50 mg/dL").
The 1800 Rule
ISF = 1800 ÷ Total Daily Insulin Dose
For instance, if TDD is 60 units, 1800/60 = 30, meaning 1 unit drops BG by ~30 mg/dL.
Correction Dose Formula
Correction Units = (Current BG - Target BG) ÷ CF
Example: Current BG 200 mg/dL, target 100 mg/dL, CF = 50 mg/dL per unit
(200-100) ÷ 50 = 2 units needed to correct
Safety Note
Correction dosing should be done cautiously: most people correct only before meals, not between meals. Always check how recent doses or active insulin might affect the correction.
Combining Carb Coverage + Correction
Getting your complete meal bolus dose
To get your total meal bolus with both carb coverage and correction:
Calculate Carb Dose
Sum the carbs (in grams) and divide by your ICR (g/unit)
Calculate Correction
(Current BG – target BG) ÷ CF
Add Together
Total units = (carb dose) + (correction dose)
Example Calculation
| Step | Calculation | Example |
|---|---|---|
| Carbs | Carbs (g) ÷ ICR (g/unit) = units | 45g ÷ 15 = 3 units |
| Correction | (Current BG – Target BG) ÷ CF = units | (190–120) ÷ 35 = 2 units |
| Total Bolus | Carbs units + Correction units | 3 + 2 = 5 units |
Safety Considerations
Critical safety information for insulin management
Preventing Hypoglycemia
- • Always carry fast-acting carbs (glucose tablets, juice) for lows
- • Follow the "15-15 rule": treat BG <70 mg/dL with ~15g glucose, recheck in 15 min
- • Never overcorrect with insulin if BG is trending low
- • If repeatedly dropping low, reduce regimen by ~10-20%
Timing Injections
- • Take rapid-acting insulin 10-15 min before meals
- • Regular insulin needs ~30 min lead time
- • Injecting after meals often causes post-meal spikes
Injection Technique
- • Use the same general area for consistent absorption
- • Rotate sites within that area
- • Avoid injecting into scarred or hard areas
Insulin on Board (IOB)
- • Track active insulin to avoid "stacking"
- • Most rapid insulins last ~3-5 hours
- • Wait 2-3 hours before another correction
- • Modern pumps and apps track IOB automatically
Special Situations
How to adjust insulin for different circumstances
Illness ("Sick Days")
Being sick triggers stress hormones that raise blood sugar:
- Monitor BG and ketones every 4-6 hours
- Continue insulin even if not eating much
- You may need MORE insulin than usual
- Stay hydrated - drink plenty of water
- Keep simple carbs available for lows
- Have a sick-day plan from your provider
Exercise
Physical activity often lowers blood glucose:
- May need to reduce mealtime insulin
- Consider eating extra carbs (15-30g per 30-60 min exercise)
- For long workouts (>30 min), consider lowering rapid dose
- Check BG before, during, and after exercise
- If active after meals, might reduce that meal's insulin
Meal Composition Effects
High-Fat Meals (Pizza, Burgers)
- Cause delayed glucose rises hours later
- Consider "dual-wave" bolus (half now, half later)
- Monitor responses by testing
Slow Carbs (Legumes, Whole Grains)
- Digest gradually, less immediate impact
- Might use smaller initial bolus
- Consider splitting the dose
Tools and Calculators
Modern technology to automate calculations and improve accuracy
Insulin Pumps
- • Built-in bolus calculators
- • Enter carbs and current BG
- • Automatically accounts for active insulin
- • Greatly reduces calculation errors
Smartphone Apps
- • mySugr Bolus Calculator
- • Carb counting apps
- • Pump-control apps
- • Connect to meters for automated entry
Blood Glucose Meters
- • Some have bolus calculator add-ons
- • FreeStyle InsuLinx example
- • Use programmed ratios and correction factors
- • Improve dose accuracy significantly
Carb Counting Aids
- • Nutrition labels and carb-counting books
- • MyFitnessPal, Fooducate apps
- • Save favorite meals
- • Specialized healthcare system apps
Research Shows
Studies show that bolus calculators improve dose accuracy and confidence: one survey found 63% of manual dose calculations were wrong, versus far fewer when using calculator tools. Bolus calculators improve post-meal control and patient confidence.
References & Sources
Authoritative sources supporting insulin dosing recommendations
[1] American Diabetes Association (ADA)
"Standards of Medical Care in Diabetes." Clinical practice guidelines for diabetes care, including intensive insulin therapy recommendations and carbohydrate counting protocols.ADA Guidelines
[2] Diabetes UK
"DAFNE Programme - Dose Adjustment For Normal Eating." Patient education resources including the DAFNE program for flexible insulin dosing and carbohydrate counting.Diabetes UK
[3] Mayo Clinic
"Diabetes management: How lifestyle, daily routine affect blood sugar." Clinical guidance on insulin therapy, timing, injection techniques, and diabetes management protocols.Mayo Clinic Guide
[4] Diabetes Care Journal
"Bolus Calculator: A Review of Four Smart Insulin Pumps." Published studies on bolus calculator effectiveness, insulin-to-carb ratios, and correction factor calculations. Diabetes Care, 2008.Diabetes Care Research
[5] Alberta Health Services
"Insulin to Carbohydrate Ratio and Correction Factor." Comprehensive insulin dosing guidelines including carbohydrate counting and correction dose protocols.AHS Guidelines
[6] NHS Guidelines
"Type 1 diabetes in adults: diagnosis and management." National Institute for Health and Care Excellence (NICE) clinical guidelines for insulin therapy and diabetes management.NHS Diabetes Guide
Important Disclaimer
These calculations are based on established diabetes care guidelines and should be used in consultation with healthcare providers. Individual insulin needs vary significantly, and all dosing decisions should be made under medical supervision. This calculator is for educational purposes and should not replace professional medical advice.