Diabetes Sick Day Rules: Common Myths and What Guidelines Say
Diabetes Sick Day Rules: what people commonly get wrong, set against what published UK guidance says.
Illness raises glucose even when you are eating less, and some medicines must be paused to avoid harm.
Key takeaways
- Illness effect: raises blood glucose even with reduced intake
- Never stop: insulin, even if you are not eating
- Most useful single change: Get written sick day rules from your diabetes team before you need them.
- Commonest mistake: Stopping insulin because you are not eating.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
What the guidance actually says
Here is what guidance actually publishes. The rest of the page is measured against it.
| Measure | Figure |
|---|---|
| Illness effect | raises blood glucose even with reduced intake |
| Never stop | insulin, even if you are not eating |
| Often paused when dehydrated | metformin, SGLT2 inhibitors, ACE inhibitors, diuretics, NSAIDs |
| Testing frequency when unwell | more often, as advised by your team |
| Ketone testing | advised for type 1 and some others when glucose is high |
Where people go wrong
What people tend to think, set against what is actually published.
- Stopping insulin because you are not eating
- Continuing metformin or SGLT2 inhibitors while vomiting or dehydrated, without advice
- Waiting to see whether things improve if ketones are raised
What to do instead
- Get written sick day rules from your diabetes team before you need them
- Keep taking insulin and test more often
- Keep fluids up, and use sugary drinks if you cannot eat
- Contact your team early rather than waiting
The part that is genuinely uncertain
Guidance changes, and it changes because evidence does. The figures above reflect current UK guidance from the bodies named at the foot of this page; where those bodies revise their position, theirs is the account to follow rather than this one.
Where to go next
- Diabetes Sick Day Rules: The Quick Reference
- Diabetes Sick Day Rules: What Published Guidance Supports
- Diabetes Sick Day Rules — the reference entry
- The Evidence on Diabetes and Driving, Without the Hype
- Diabetes Remission: What the Evidence Actually Says
When to speak to a doctor
Seek urgent medical help for persistent vomiting, raised ketones, deep or rapid breathing, breath smelling of pear drops, abdominal pain, drowsiness or confusion — these can indicate diabetic ketoacidosis, which is a medical emergency. Contact your diabetes team the same day if you cannot keep fluids down.
Where this comes from
- Diabetes UK — sick day rules
- NICE — Type 2 diabetes in adults: management
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
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