Insulin Dose Calculator
Work through the standard starting rules for total daily insulin, carbohydrate ratio and correction factor — all of which a clinician must then titrate.
Insulin Dose Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- The 500 and 1,800 rules are population averages, not individual measurements.
- Does not model insulin on board, pump basal profiles or variable ratios by time of day.
- Cannot account for illness, steroids, exercise or cycle-related sensitivity changes.
In short: At 0.5 units/kg an 80 kg adult starts near 40 units a day, split 20 basal and 20 bolus. The 500 rule gives a carbohydrate ratio of 1 unit per 12.5 g and the 1,800 rule a correction factor of 45 mg/dL per unit — starting points only, never a prescription.
Formula
Use 1,500 rather than 1,800 for regular insulin. All are empirical starting points.
Worked Example
- Estimate the total daily dose. 80 kg × 0.5 units/kg = 40 units a day.
- Split basal and bolus. 50/50 gives 20 units basal and 20 units bolus across meals.
- Apply the 500 rule. 500 ÷ 40 = 1 unit per 12.5 g of carbohydrate.
- Apply the 1,800 rule. 1,800 ÷ 40 = 45 mg/dL per unit.
- Work the correction. (210 − 120) ÷ 45 = 2.0 units, plus 4.8 for a 60 g meal.
Every figure on this page is a starting point that gets titrated away. The 500 and 1,800 rules are empirical constants fitted to population averages, and they carry no information about the individual in front of them. Real insulin sensitivity moves with illness, steroids, cycle phase, sleep, injection site and exercise — which can keep lowering glucose for many hours after it finishes. Someone with marked insulin resistance may need two or three times the 0.5 units/kg starting factor, and someone in the honeymoon phase of type 1 far less. The rules exist to give a clinician somewhere to begin on day one; by week four the numbers should have moved, and if they have not, the titration is not happening.
Strengths & Limits Of This Model
Where this engine is strong
- Shows how the ratio and correction factor both derive from the total daily dose.
- Refuses to compute a correction during hypoglycaemia and directs to carbohydrate.
- States the stacking window explicitly.
Where it stops
- Cannot personalise beyond population rules.
- Cannot replace titration against real glucose records.
Practical Use Cases
Understanding how a starting regimen is derived
Weight sets the total, the total sets the ratio and the correction factor.
Following a clinic conversation
These are the rules your team is working from when they propose a starting dose.
Seeing why the correction factor changes
It is 1,800 divided by the total daily dose, so any change in the total moves it.
Checking basal proportion
Around half is conventional. See the Basal Insulin Calculator.
Methodology & Editorial Standards
This engine reproduces the standard published rules used to construct a starting insulin regimen, and frames every output as a starting point subject to titration rather than a dose. Total daily dose is estimated from body weight using a units-per-kilogram factor, conventionally around 0.5 for an adult beginning therapy, with markedly higher values in insulin resistance and lower values during the honeymoon phase of type 1 diabetes. The total is divided between long-acting basal and rapid-acting bolus insulin, conventionally in equal shares. The carbohydrate ratio follows the 500 rule and the correction factor the 1,800 rule, both empirical constants divided by the total daily dose; the 1,500 rule replaces 1,800 where regular rather than rapid-acting insulin is used. Because both derive from the total, any change to the total moves them together. The engine enforces a hypoglycaemia stop-rule, refusing to compute a correction below 70 mg/dL and directing the user to fast-acting carbohydrate instead, and it warns about insulin stacking, since rapid-acting insulin remains active for four to five hours and a correction layered on top of one still working is a recognised cause of severe hypoglycaemia. Insulin is a high-alert medicine and no output here constitutes a prescription. This calculator is an educational estimate and is not medical advice, diagnosis, treatment or a prescription. It performs arithmetic on values you enter and cannot assess your clinical condition. Never start, stop, change or skip a dose of any medicine on the basis of a number produced here. Dose selection belongs to a prescriber working from the approved product label, your full medication list and your current clinical state. If you are acutely unwell, dehydrated, vomiting, or your kidney function is changing, estimating equations are unreliable and urgent clinical review is required. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Insulin Dose Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How is total daily insulin estimated?
Body weight times a units-per-kilogram factor, often 0.5 to start. It is a starting point, not a target.
What is the 500 rule?
Carbohydrate ratio = 500 ÷ total daily dose. At 40 units a day that is 1 unit per 12.5 g.
What is the 1,800 rule?
Correction factor = 1,800 ÷ total daily dose. At 40 units that is 45 mg/dL per unit.
When is the 1,500 rule used instead?
For regular rather than rapid-acting insulin, which is less potent per unit over the correction window.
What is the basal-bolus split?
Conventionally about half long-acting background insulin and half rapid-acting across meals.
Should I correct a low glucose with insulin?
Never. Below 70 mg/dL requires 15 g of fast-acting carbohydrate and a retest in 15 minutes.
What is insulin stacking?
Adding a correction while a previous rapid-acting dose is still working. It is a common cause of severe hypos.
How long does rapid-acting insulin last?
Four to five hours. That whole period must be considered before adding another correction.
Why do my requirements change?
Illness, steroids, cycle phase, sleep, stress, injection site and exercise all shift insulin sensitivity.
Does exercise lower insulin needs?
Yes, often for many hours afterwards, which is why post-exercise hypos frequently happen overnight.
Is 0.5 units/kg right for type 2 diabetes?
Often not. Marked insulin resistance can require substantially more. It is a starting figure only.
Can I change my own doses using this?
No. Insulin is a high-alert medicine. Regimen changes belong to your diabetes team.
Why does the correction factor change when my total changes?
Because it is 1,800 divided by the total. A larger total daily dose implies greater sensitivity per unit.
What target glucose should I use?
Individualised by your team. Tighter targets raise hypo risk, which is why they are not universal.
Does this work with a pump?
The same rules underpin pump settings, but pumps use basal rates and additional parameters this does not model.
What if my glucose is very high?
Persistent very high readings, especially with ketones, vomiting or breathlessness, need urgent medical care, not a correction dose.
Is this insulin dose calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.