What insulin rate does this use?

It uses the JBDS fixed-rate intravenous insulin infusion of 0.1 units per kilogram per hour, made up as 50 units of soluble insulin in 50 mL of 0.9% sodium chloride. The displayed rate in mL/hour equals the units/hour because the mixture is 1 unit per mL.

How is the first litre handled if blood pressure is low?

If the systolic blood pressure is below 90 mmHg the protocol gives a 500 mL bolus of 0.9% sodium chloride over 10 to 15 minutes, repeated if needed, before starting the timed replacement bags. The tool flags this and starts the timed schedule afterwards.

Why does potassium depend on the serum level?

Insulin drives potassium into cells and can cause dangerous hypokalaemia. The protocol adds 40 mmol potassium chloride per litre when serum potassium is 3.5 to 5.5 mmol/L, no potassium above 5.5, and senior review with more aggressive replacement below 3.5.

Does this replace clinical judgement?

No. It reproduces the standard adult JBDS schedule for a typical case. Pregnancy, young adults, heart or kidney failure, and very high or low presentations need senior input and individualised fluid rates, which this tool does not model.

When should the fluid bags be slowed?

The staged schedule front-loads fluid then slows as the deficit is corrected. Caution and slower rates apply in the elderly, in pregnancy, and where there is a risk of cerebral oedema or fluid overload, so reassess clinically at each bag change.

What is the DKA IV Fluid Regime Calculator?

Applies the JBDS DKA protocol to compute 0.9% sodium chloride fluid volumes across the first hours of treatment, potassium chloride additions by serum potassium band, and a fixed-rate insulin infusion from weight. For acute medical and ED teams. It runs free in your browser on Gera Tools, with nothing uploaded.

DKA IV Fluid Regime Calculator

Name: DKA IV Fluid Regime Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Diabetic ketoacidosis is treated with prompt fluid resuscitation, a fixed-rate insulin infusion, and careful potassium replacement. This calculator reproduces the standard adult schedule used across UK acute units so you can read the insulin rate, the staged saline volumes, and the potassium addition for a given patient at a glance.

How it works

The regime has three parts that run together:

Insulin   = 0.1 units/kg/hour, made as 50 units in 50 mL 0.9% NaCl
            (so mL/hour = units/hour)
Fluids    = 0.9% sodium chloride in timed bags:
            1 L over 1 h, 1 L over 2 h, 1 L over 2 h, 1 L over 4 h,
            1 L over 4 h, 1 L over 6 h
            (if systolic BP < 90 mmHg: give 500 mL bolus first)
Potassium = serum K > 5.5  -> none
            serum K 3.5-5.5 -> 40 mmol KCl per litre
            serum K < 3.5   -> senior review, >40 mmol/L needed

The insulin mixture is deliberately one unit per millilitre, so a pump rate in millilitres per hour reads the same as the units-per-hour dose.

Example and notes

An 80 kg patient with a systolic blood pressure of 110 mmHg and a serum potassium of 4.2 mmol/L receives an 8 units/hour fixed-rate insulin infusion, the timed litre bags of 0.9% sodium chloride, and 40 mmol of potassium chloride added to each litre from the second bag onward. Always recheck potassium hourly at first, watch for cerebral oedema in younger patients, and slow the fluids for frail or cardiac patients. This tool is a bedside aid, not a substitute for the full protocol or senior review.

Clinical context and common questions

Why a fixed-rate insulin infusion rather than a sliding scale?

Earlier DKA protocols used variable-rate insulin infusions adjusted to blood glucose. The JBDS (Joint British Diabetes Societies) moved to a fixed-rate infusion because: the primary goal of insulin in DKA is to switch off ketone production, not just lower blood glucose; the dose needed to suppress ketogenesis is predictable per kilogram; and a fixed rate simplifies preparation, reduces prescription errors, and avoids under-dosing when glucose is falling quickly. Once the patient’s blood glucose drops below 14 mmol/L, 10% glucose is typically co-infused rather than the insulin being slowed, maintaining the anti-ketogenic effect while preventing hypoglycaemia.

The first bag decision: why blood pressure matters

The protocol splits the initial fluid approach based on circulatory status. In DKA, patients are often substantially dehydrated — the average fluid deficit is several litres — and a systolic blood pressure below 90 mmHg indicates haemodynamic compromise that must be corrected urgently. A fast 500 mL bolus of 0.9% sodium chloride given over 10–15 minutes and repeated if necessary restores circulating volume before the timed replacement schedule begins. If blood pressure is adequate (systolic ≥ 90 mmHg), the bolus is omitted and the replacement goes straight into the timed bag schedule.

Potassium management — the highest-stakes part of the regime

Insulin drives potassium into cells. In DKA, serum potassium before treatment is often falsely elevated — the acidosis pushes potassium out of cells, masking the body’s true potassium deficit. Once insulin is started and the acidosis begins to correct, potassium moves back into cells and serum levels can fall sharply and rapidly. The JBDS potassium bands are:

K above 5.5 mmol/L — no potassium added to bags; recheck frequently.
K between 3.5 and 5.5 mmol/L — add 40 mmol KCl per litre of fluid.
K below 3.5 mmol/L — insulin must be paused or carefully titrated; senior or specialist input is required; more aggressive replacement is needed before insulin is safely continued.

This tool flags the third scenario with a specific warning because continuing insulin without correcting severe hypokalaemia risks fatal arrhythmia.

Which patients need a modified approach

The standard JBDS adult protocol is designed for typical presentations. Several categories of patient require deviation and should involve senior or specialist input from the outset:

Children and young adults (under 18 or ~25 in some centres): lower fluid rates to reduce cerebral oedema risk.
Pregnant women: specialist obstetric and diabetes input; different fluid and potassium targets.
Patients with cardiac failure or renal failure: slower fluid replacement to avoid pulmonary oedema.
Very elderly or frail patients: slower fluid replacement and more frequent reassessment.
Patients with mixed hyperosmolar hyperglycaemic state (HHS) and DKA: different fluid composition and targets.