How to use the Insulin Dosing Calculator: step-by-step guide

What this calculator does

This calculator helps you estimate two common components of a rapid-acting insulin bolus: the insulin needed to cover carbohydrates in a meal (the insulin-to-carbohydrate ratio, or ICR) and the insulin needed to correct elevated blood glucose (the correction factor, sometimes called insulin sensitivity factor or ISF). It uses commonly adopted estimation rules (for example, ICR ≈ 500 ÷ total daily insulin dose and ISF ≈ 1700 ÷ total daily dose) and instantly shows a visual breakdown so you can see how much of the final dose is carb cover vs correction. Healthline+1

Inputs the calculator needs

1. Current blood glucose (mg/dL) — your most recent fingerstick or CGM reading.
2. Target blood glucose (mg/dL) — the glucose level you and your clinician have agreed is appropriate pre-meal.
3. Carbohydrates (grams) — total grams of carbohydrate in the meal or snack.
4. Total Daily Dose (TDD) of insulin (units) — your average daily total insulin (basal + bolus). This is used to estimate ICR and ISF if you do not provide them manually. diabetesteachingcenter.ucsf.edu

You may optionally enter your own ICR or correction factor if your clinician has already personalised them. The tool will auto-calculate ICR (500 ÷ TDD) and correction (1700 ÷ TDD) when you leave those fields blank — these are starting formulas widely used in clinical practice and education. Healthline+1

How the maths works (simple explanation)

• Carb insulin = carbohydrates (g) ÷ ICR (g covered by 1 unit). Example: if ICR = 10 g/U and you eat 60 g carbs → carb insulin = 6 U. Western Carolina University | Home
• Correction insulin = (current BG − target BG) ÷ ISF (mg/dL lowered by 1 unit). Example: if current BG is 200 mg/dL, target 120 mg/dL, and ISF = 40 mg/dL per unit → correction = (200−120) ÷ 40 = 2 U. Texas Children’s
• Total bolus = carb insulin + correction insulin (rounded to a practical precision you normally use).

The calculator performs those computations for you, displays the numeric results, and creates a Plotly pie chart that shows how much of the bolus comes from carb coverage vs correction — a quick visual that helps you check the balance.

Practical tips for accurate use

• Know your TDD. Accurate TDD gives better auto-estimates for ICR and ISF. If you’re unsure, use documented daily averages from your pump or insulin log. diabetesteachingcenter.ucsf.edu
• Measure carbs carefully. Use labels, apps, or food scales when possible; manual carb counting errors are a common reason for mismatches.
• Round sensibly. Many people round to the nearest 0.5 or 1.0 unit depending on their device; adjust the calculator output accordingly.
• Always follow your care team. These rules are educational estimates and need clinician confirmation. The calculator is not a prescription. American Diabetes Association

Interpreting the Plotly visual

The built-in Plotly chart displays a two-slice pie: one slice for the carb bolus and one slice for correction insulin. The chart’s annotation shows the total units. This helps you quickly recognise whether a large proportion of your dose is a correction (suggesting high starting glucose) or carb cover (large meal).

When not to use the calculator

• If you are sick, have vomiting, or are ketotic — follow emergency instructions from your healthcare team.
• If you have rapid changes in insulin sensitivity (e.g., hormonal changes, new medication, recent exercise) — consult your clinician before relying on automated estimates. These rules are not replacements for clinical judgement. Royal Children’s Hospital

Privacy & technical notes

No data is stored by the widget by default — it runs client-side in the browser. If you embed the code in WordPress, host pages should be served securely (HTTPS). The calculator uses Plotly.js (client side) to create the visual; ensure Plotly scripts are allowed on your site.

Disclaimer

This calculator provides educational estimates only. It is not medical advice and does not replace personalised dosing instructions from a healthcare professional. Always consult your diabetes care team before changing insulin doses. If you experience persistent high glucose, hypoglycaemia, or ketones, follow emergency medical guidance. The formulas used (ICR ≈ 500 ÷ TDD; ISF ≈ 1700 ÷ TDD) are widely used starting rules but must be personalised; they are not precise for every individual. Healthline+1

FAQ

Q: What if my units per carbohydrate (ICR) are very different from the auto-calculated value?
A: Enter your clinician-prescribed ICR manually. Auto-calculation is only a starting estimate; many people have unique ratios by time of day that should override defaults.

Q: Which rule should I use — 500 or 450, 1700 or 1800?
A: Several similar rules exist (450 vs 500, 1500 vs 1700 vs 1800). They are heuristics. The best approach is to start with one rule and refine using glucose logs under clinician guidance. Clinical guidelines and expert consensus discuss ranges and individualized approaches. Diabetes Journals+1

Q: Can I use this tool for children or pregnancy?
A: Paediatric and pregnancy dosing are specialised. Use only under supervision of a paediatric endocrinologist or obstetric diabetes specialist.

Q: Is my data saved when I use the calculator?
A: The provided widget runs client-side; it does not send values to external servers. Confirm any site-specific customisations if you add analytics or server-side logging.

Q: How accurate will the visualisation be?
A: The Plotly visual shows the numerical outputs supplied by the calculator. It helps interpret dose composition but does not change the underlying calculation.

References / further reading

Key educational sources for the methods used: UCSF Diabetes Teaching Center (calculating insulin dose), patient education materials on insulin-to-carbohydrate ratios and correction factors, and guidance summaries from diabetes organisations. diabetesteachingcenter.ucsf.edu+2Western Carolina University | Home+2