Insulin Correction Dose Calculator — Correction Factor & 1800/1500 Rule
The insulin correction dose (also called correction bolus or supplemental dose) is the amount of rapid-acting insulin needed to bring elevated blood glucose down to target level, based on the individual's insulin sensitivity factor (correction factor).
About
The insulin correction dose is calculated using the insulin sensitivity factor (ISF), also known as the correction factor, which represents how much 1 unit of rapid-acting insulin lowers blood glucose (in mg/dL). The correction factor can be determined clinically by the 1800-rule (for rapid-acting insulin analogs like lispro, aspart, glulisine) or the 1500-rule (for regular insulin). Correction Dose = (Current BG - Target BG) / Correction Factor. For example, if current BG is 250 mg/dL, target BG is 100 mg/dL, and the correction factor is 50 mg/dL per unit, the correction dose would be (250-100)/50 = 3 units. The correction dose should be administered in addition to meal-time insulin if the pre-meal BG is above target. Some protocols use a more conservative approach for high BG levels (e.g., giving half the calculated dose if BG >300 or administering the calculated dose and rechecking in 2 hours). Patients with a history of hypoglycemia, renal impairment, or those on insulin pumps may require modified correction algorithms.
Formula
Correction Dose (units) = (Current BG - Target BG) / Correction Factor (mg/dL per unit)
The correction factor (also called insulin sensitivity factor) can be estimated using the 1800-rule: ISF = 1800 / Total Daily Dose (TDD). For example, a patient with TDD of 60 units has an ISF of 1800/60 = 30 mg/dL per unit. Alternatively, the 1500-rule (ISF = 1500/TDD) is used for regular human insulin. The calculated dose should be rounded to the nearest 0.5 unit for insulin pens or 1 unit for syringes.
Score Interpretation
Insulin correction dosing is a fundamental component of intensive insulin therapy, enabling patients to achieve glycemic targets while minimizing hypoglycemia risk. The correction factor approach, combined with the 1800/1500 rule estimates, provides a systematic method for determining appropriate insulin doses that can be adjusted based on individual patient response. Correction dosing is used in both type 1 and type 2 diabetes, in inpatient and outpatient settings, and is a core component of insulin pump therapy, multiple daily injection (MDI) regimens, and inpatient insulin protocols.
No Correction Needed — 0–0
Current BG is at or below target. No insulin needed.
Management: No correction insulin. Monitor as scheduled.
Standard Correction — 0.1–5
Standard correction dose. Safe range for administration.
Management: Administer correction dose. Recheck BG in 2-4 hours.
Moderate Correction — 5.1–10
Moderate correction dose. Monitor for hypoglycemia.
Management: Consider splitting dose if >8 units. Monitor BG closely.
Large Correction — 10.1+
Large correction dose. High risk of hypoglycemia.
Management: Consider giving partial dose and rechecking BG in 2 hours. Monitor for hypoglycemia closely. Evaluate for causes of severe hyperglycemia.
Reference Ranges
| Population | Normal Range | Notes |
|---|---|---|
| Adults with diabetes on insulin therapy | Based on individual ISF | ISF typically 15-80 mg/dL per unit; higher ISF = less insulin needed |
Dr. Khaled Hassan
Dr. Khaled is a cardiology consultant with experience in acute cardiac care.
View medical review board & editorial policy →Example Calculation
A patient with type 1 diabetes uses a correction factor of 40 mg/dL per unit. Pre-lunch BG is 240 mg/dL and target is 120 mg/dL. Correction dose = (240 - 120) / 40 = 120/40 = 3 units. If the patient's TDD is 45 units, the 1800-rule estimate would be: ISF = 1800/45 = 40 mg/dL per unit, confirming the prescribed factor.
Related Conditions
Related Medications
Common Mistakes
Administering the full calculated dose when BG is very high (>400 mg/dL)
For BG >400 mg/dL, consider giving half the calculated dose and rechecking in 2 hours. This reduces risk of rapid glucose drop and hypoglycemia.
Not accounting for residual insulin (insulin stacking)
When giving correction doses within 3-4 hours of a previous insulin dose, account for remaining active insulin. Insulin stacking can cause severe hypoglycemia.
Frequently Asked Questions
What is the 1800-rule and when should I use it?
Should I always give the full correction dose?
References
- Davidson PC, Hebblewhite HR, Steed RD, et al. Analysis of guidelines for basal-bolus insulin dosing: basal insulin, correction factor, and carbohydrate-to-insulin ratio. Endocr Pract. 2008;14(9):1095-1101. PubMed
- American Diabetes Association. Standards of Care in Diabetes — 2025. Diabetes Care. 2025;48(Suppl 1):S1-S306.
- Walsh J, Roberts R, Varma C, et al. Using insulin: everything you need for success with insulin. 2nd ed. San Diego: Torrey Pines Press; 2003.