Feeling Unwell on Insulin

1

Safety

The Golden Rule & the DKA Red Flags

Done

DO NOT STOP TAKING YOUR INSULIN — even if you are unable to eat. You need food, insulin and fluids together to avoid dehydration and serious complications. Then watch for the signs that mean hospital.

Blood ketones > 3.0 mmol/L (or +++/++++ on urine) → high risk of established DKA → urgent hospital assessment.

Blood ketones > 1.5 mmol/L → high risk of DKA → consider urgent hospital assessment; treat with extra insulin and recheck every 2h meanwhile.

Vomiting / can't keep fluids down → can't maintain hydration or carbohydrate → seek urgent medical advice / admission.

DKA symptoms Thirst, polyuria, dehydration, laboured breathing, abdominal pain, nausea/vomiting, drowsiness/confusion, pear-drop breath → emergency.

Can't control glucose or ketones Despite extra insulin → escalate; don't keep cycling alone.

Unsure how to adjust the dose → contact the diabetes specialist team or GP for advice rather than guessing.

Insulin is never stopped during illness because the stress hormones of any acute illness drive glucose and ketone production up — the body needs more insulin, not less, even when the patient isn't eating. Stopping insulin (often because of poor appetite) is the single commonest avoidable cause of DKA, and a blood ketone above 1.5 mmol/L is the practical "this could become DKA" alarm.

2

Diagnose

Test — Glucose & Ketones, More Often

Done

Type 1 diabetes

Test blood glucose AND ketones every 4–6 hours, including through the night.

Type 2 on insulin

Test blood glucose at least 4 times a day; add ketone testing if glucose >11 and unwell.

Step up to 2-hourly if…

Glucose >11 mmol/L and/or ketones present (>1.5 mmol/L blood, or +/++ urine) → test glucose and ketones every 2 hours, including overnight.

Ketone bands

Blood <0.6 normal · 0.6–1.5 act/recheck · 1.5–3.0 high risk · >3.0 urgent. Urine: +/++ ≈ 1.5–3.0; +++/++++ >3.0.

Prefer blood ketones

A blood ketone meter is more reliable and timely than urine sticks for sick-day decisions.

Frequent testing — including overnight — is what catches a rising ketone trend before it tips into DKA. The 2-hourly cycle for glucose >11 with ketones is deliberately intensive because that's the window in which extra insulin can still reverse ketogenesis at home.

3

Treat

Two Ways to Add Insulin — Pick by Ketone Level

Done

Give extra insulin on top of the usual regimen. Which method depends on whether ketones are present.

BG >11, no / low ketones (<1.5)

Method A — extra units per dose

Add a fixed number of extra units to each usual insulin dose, scaled by glucose (Step 4). Test BG every 4h.

Ketones present (>1.5, or +/++ urine)

Method B — % of total daily dose

Give extra rapid-acting/mixed insulin every 2 hours as a percentage of total daily dose (Step 5). Higher % if ketones higher.

Always

Continue usual insulin + basal

Extra doses are additional — keep taking the normal basal/bolus or mixed insulin as prescribed.

If on a pump

Correction boluses + check set

Give correction boluses; if ketones rising despite correction, suspect a failed set/site → switch to pen and follow Method B.

Ketones change the dosing logic: without ketones, a modest fixed top-up per dose corrects hyperglycaemia; with ketones, you need larger, more frequent rapid-acting doses to switch off ketone production, which is why the percentage-of-total-daily-dose method is used. Keeping the usual basal running underneath both is essential — basal insulin is what prevents ketogenesis in the first place.

4

Treat

Method A — Extra Units by Glucose (no / low ketones)

Done

When glucose is >11 with no or only trace ketones, add fixed extra units to each insulin dose:

11–17Add 2 extra units to each dose

17–22Add 4 extra units to each dose

>22Add 6 extra units to each dose

>50 u/dayIf total daily insulin >50 units, double these adjustments (+4 / +8 / +12)

ℹ️ Take your prescribed insulin plus these increments. All adjustments are incremental and should be reduced gradually as the illness subsides. Once you've given the initial increased dose, contact your GP or DSN for advice if still unsure. Recheck glucose every 4 hours (every 2 hours if ketones appear).

The fixed-increment table (from TREND-UK / Diabetes & Primary Care) gives patients a safe, simple correction without needing to calculate ratios while feeling unwell. The doubling rule above 50 units/day accounts for the relative insulin resistance of higher-requirement patients, in whom small fixed increments would be inadequate.

5

Treat

Method B — % of Total Daily Dose (ketones present)

Done

When ketones are present with BG >11, give extra rapid-acting or mixed insulin every 2 hours as a percentage of total daily dose. Use +10% for ketones up to ++ (1.5–3.0) and +20% for +++/++++ (>3.0):

Up to 14u+10% → give 1 unit every 2h · +20% → give 2 units every 2h

15–24u+10% → give 2 units every 2h · +20% → give 4 units every 2h

25–34u+10% → give 3 units every 2h · +20% → give 6 units every 2h

35–44u+10% → give 4 units every 2h · +20% → give 8 units every 2h

45–54u+10% → give 5 units every 2h · +20% → give 10 units every 2h

ℹ️ Total daily dose >54 units, or unsure how to alter the dose → contact your specialist team or GP. Recheck blood glucose & ketones every 2 hours and repeat the extra dose until BG <11 and ketones clear. Drink plenty of water to flush ketones.

Dosing by percentage of total daily dose scales the correction to the patient's own insulin requirement, and the 2-hourly rapid-acting schedule provides the sustained extra insulin needed to suppress ketogenesis. The cut-off at >54 units (and the advice to call the team) reflects that very high-requirement or brittle patients need specialist input rather than an off-the-shelf table.

6

Treat

Carbohydrate & Fluids Alongside the Insulin

Done

If BG <11 & no ketones

Take insulin as normal. Take carbohydrate as a meal replacement and sip sugar-free liquids (≥100 mL/hour if able).

If BG >11

Continue insulin + extra doses; maintain fluids with sugar-free drinks to rehydrate without raising glucose further.

If unable to eat / vomiting

Replace meals with sugary fluids or easy carbs (soup, milk, yoghurt, ice cream) to keep calories up.

If BG runs low

Switch to sugary fluids to keep glucose up — but never omit basal insulin.

Volume

Sip at least 100 mL/hour if able; small frequent sips if nauseated.

Ketones present

Drink plenty of water to maintain hydration and flush ketones, alongside the extra insulin.

Insulin alone isn't enough — without carbohydrate the patient risks hypoglycaemia from the extra doses, and without fluids they dehydrate and concentrate ketones. Matching fluid type to glucose (sugary when low/not eating, sugar-free when high) keeps both glucose and hydration in range.

7

Lifestyle

As the Illness Resolves — Step the Dose Back Down

Done

Taper extra insulin gradually As illness resolves, adjust insulin dose back to normal — reduce the increments incrementally rather than stopping abruptly.

Watch for hypos As appetite and wellbeing return, the extra insulin can cause hypoglycaemia — reduce promptly and keep fast-acting carbs to hand.

Keep testing until stable Continue more frequent glucose (± ketone) checks until back to baseline, then resume the usual routine.

Return to usual regimen Once eating, drinking and glucose are back to normal, return fully to the prescribed insulin doses.

Debrief if it was severe If the episode needed big dose changes or nearly led to admission, review with GP/DSN and refresh the sick-day plan.

Restock the kit Replace used ketone strips and check expiry dates so the kit is ready for next time.

The recovery taper matters because the insulin requirement falls as the illness (and its stress hormones) settle — continuing sick-day doses into recovery is a common cause of rebound hypoglycaemia. Tapering incrementally, while still testing, lands the patient safely back on their usual regimen.

8

Refer

When to Seek Urgent Advice or Admit

Done

999 / admit

Blood ketones >3.0 mmol/L (or +++/++++), suspected DKA, reduced consciousness, or severe dehydration → emergency admission.

Urgent advice

Start vomiting, unable to keep fluids down, or unable to control glucose/ketones → SEEK URGENT MEDICAL ADVICE.

Ketones >1.5 mmol/L

High risk of DKA → consider urgent hospital assessment while continuing extra insulin and 2-hourly checks.

Unsure how to adjust

Total daily dose >54 units, or any uncertainty about altering doses → contact specialist team / GP.

Not improving

Persistent hyperglycaemia/ketones despite extra insulin, or clinical deterioration → escalate.

High-risk patient

Recent DKA, hypoglycaemia unawareness, pregnancy, frailty, CKD → lower threshold to seek help.

The escalation triggers are deliberately concrete — vomiting, ketones above 1.5–3.0, uncontrolled glucose — because these are the points at which home management is failing and DKA becomes likely. A patient who can't keep fluids down can't out-drink their losses and needs IV fluids and insulin.

9

Safety

Key Safety Points & Patient Preparation

Done

Never stop insulin The single most important message — even when not eating. Basal insulin in particular prevents ketogenesis.

Extra doses are additional Always on top of the normal regimen, incremental, and tapered as illness resolves.

Blood ketone meter + strips Ensure the patient has an in-date meter and strips at home before they're ill.

Know the numbers Ketones >1.5 = seek advice; >3.0 = hospital. Glucose >11 = step up testing & add insulin.

Written plan + contacts TREND-UK leaflet, GP/DSN/out-of-hours/111 numbers, and the dose tables printed out.

SADMAN awareness If also on metformin/SGLT2i/ACEi/ARB/diuretic/NSAID, pause those when dehydrated (see Sick Day Rules pathway).

Insulin sick-day rules are useless if the patient doesn't have the kit and the plan before they fall ill. Equipping them with a blood ketone meter, the dose tables, clear numeric triggers and contact numbers — and reinforcing "never stop insulin" — is what prevents the predictable slide into DKA.