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Diabetes

Preventing diabetic ketoacidosis (DKA): ketone testing and sick day rules

Diabetic ketoacidosis (DKA) is a serious but largely preventable emergency in people with diabetes who use insulin. This guide explains the situations that can trigger it, how and when to test for ketones, what the NHS says about ketone levels and sick day rules, and when to call 999 or your diabetes team.

Last checked: 2026-10-10

Key facts

At a glance.

  • Serious but preventable

    The NHS says DKA is a serious condition that can be life threatening and needs urgent treatment in hospital, and gives practical steps to reduce the risk.

  • Who it affects

    The NHS says DKA usually affects people with type 1 diabetes, but can also happen in people with type 2 diabetes who need insulin. It can be the first sign of undiagnosed type 1 diabetes, particularly in children.

  • Ketone levels are a guide

    For blood ketones, the NHS gives under 0.6 mmol/L as normal and over 3 mmol/L as high, meaning you may have DKA. Your own care team may set different levels for you.

  • Never stop insulin

    The NHS says not to stop taking insulin even if you are not eating, and not to skip insulin doses.

  • Test when unwell

    The NHS advises testing for ketones when your blood glucose is high and when you are ill, and following the sick day rules your care team has given you.

  • Kit is available

    The NHS says you can get ketone testing kit free from the NHS, or buy it from a pharmacy.

Why DKA happens

Diabetic ketoacidosis happens when a lack of insulin causes harmful substances called ketones to build up in the blood. The NHS says it usually develops over about 24 hours, though it can be faster.

This page focuses on prevention. For the emergency treatment of DKA in hospital, see the related protocol page linked at the end. The NHS says treatment involves insulin, fluids and nutrients through a drip, and monitoring for complications that can sometimes affect the brain, heart or lungs.

Situations that raise the risk

The NHS lists causes of DKA as being unwell, having an injury or surgery, having your period, or not taking enough insulin. In practice this means that the days when you are least able to follow your usual routine are the days you most need to check. People may also first present with DKA when they have not yet been diagnosed with diabetes.

Because illness is such a common trigger, NICE guideline NG17 on type 1 diabetes in adults recommends considering ketone monitoring (blood or urine) as part of "sick-day rules" to help with self-management of high blood glucose.

Checking glucose and ketones

If you test urine strips, the NHS says that over 2+ is high and means you may have DKA, so you should call 999 or go to A&E. It stresses that normal blood ketone levels can differ between people, so follow the numbers your own diabetes care team has given you.

The NHS advises that if you have diabetes and any symptoms of DKA, you should check your blood glucose and, if it is high, test for ketones if you can. You can use a ketone meter to test your blood, some blood glucose monitors that also test for ketones, or strips to test your urine.

Blood ketone levels and the actions the NHS gives (a guide; your own care team may advise different levels)
Blood ketone levelWhat it meansWhat the NHS says to do
Under 0.6 mmol/LNormalNo action needed for ketones
0.6 to 1.5 mmol/LSlightly highTest again in 2 hours; get help if you feel unwell
1.6 to 3 mmol/LAt risk of DKASpeak to your diabetes care team for advice, even if you do not feel unwell
Over 3 mmol/LHigh; you may have DKACall 999 or go to A&E

Sick day rules in practice

The NHS says people with type 1 diabetes should follow guidelines from their care team on what to do when ill and how to adjust insulin (sick day rules). Its list of practical steps to reduce the risk of DKA is:

  • Follow the treatment plan agreed with your diabetes care team, including adjusting insulin when you need to.

  • Check your blood glucose regularly. The NHS type 1 diabetes advice is to check at least 4 times a day, and more often when you are unwell.

  • Ask your care team about a continuous glucose monitor or flash monitor if you do not already have one.

  • Test for ketones when your blood glucose is high and when you are ill.

  • Contact your care team if you are not sure what to do.

  • Do not stop insulin, even if you are not eating, and do not skip doses.

When to ask for help

The NHS gives two levels of advice. Call your diabetes care team or NHS 111 now if your blood glucose is high and your insulin treatment is not reducing it, even if your ketones are normal; if your ketones are slightly high (0.6 to 1.5 mmol/L) and you feel unwell; or if your ketones are 1.6 to 3 mmol/L, even if you feel well.

Call 999 or go to A&E if you have a high ketone level (over 3 mmol/L in blood or over 2+ in urine), if you do not know your ketone levels but have symptoms of DKA, or if you have symptoms and have not been diagnosed with diabetes. Symptoms the NHS lists include thirst, needing to pee more often, stomach pain, feeling or being sick, diarrhoea, breathing more deeply than usual, fruity-smelling breath, tiredness, sleepiness or confusion, and blurred vision. Do not drive to A&E; ask someone to drive you or call an ambulance, and bring your medicines.

After an episode

If you have been admitted with DKA, the NHS says you can go home once your ketones are at a safe level and you can eat and drink normally, and that doctors will talk to you about what caused it and how to reduce the risk of it happening again. This is a good time to ask for a review of your sick day rules, a refresher on insulin adjustment, and a check that you have the right ketone testing equipment at home.

Living with type 1 diabetes involves a lot of planning. The NHS notes that constantly trying to meet blood glucose targets can lead to burnout, and that with the right treatment and support people can eat normally and carry on with work and everyday life. If you find it hard to keep up with testing or injections, tell your team rather than stopping treatment.

NHS and private care in general terms

On the NHS, ketone testing advice and sick day rules are provided by the diabetes team or diabetes specialist nurse, and the NHS says ketone testing kit is available free. Private diabetes clinics may also provide education and monitoring technology, but emergency treatment for DKA is delivered in hospital, and the same ketone thresholds and 999 advice apply whichever route you use.

Frequently asked

Questions people ask.

Quick, plain-English answers to the questions we hear most.

  • Can I get DKA with type 2 diabetes?

    The NHS says DKA usually affects people with type 1 diabetes, but it can also happen in people with type 2 diabetes who need insulin.

  • What ketone level means I need emergency help?

    The NHS says over 3 mmol/L in blood, or over 2+ in urine, is high and means you may have DKA, so call 999 or go to A&E. Your own team may give you different levels.

  • What should I do if my ketones are slightly raised?

    The NHS says 0.6 to 1.5 mmol/L is slightly high; test again in 2 hours, and call your diabetes care team or NHS 111 if you feel unwell. At 1.6 to 3 mmol/L speak to your care team even if you feel well.

  • Should I take less insulin if I am not eating?

    No. The NHS says not to stop insulin even if you are not eating and not to skip doses. Ask your care team how to adjust your doses when you are ill.

  • How do I test for ketones?

    The NHS says you can use a blood ketone meter, some blood glucose monitors that also test ketones, or urine strips. Kit is available free from the NHS or can be bought at a pharmacy.

  • When should I test?

    The NHS advises testing when your blood glucose is high and when you are ill, and any time you have symptoms of DKA.

  • What are the symptoms of DKA?

    The NHS lists thirst, needing to pee more, tummy pain, feeling or being sick, diarrhoea, deep breathing, fruity-smelling breath, tiredness or confusion, and blurred vision.

  • How fast does DKA develop?

    The NHS says symptoms usually develop over 24 hours, but it can be faster, which is why early testing and quick action matter.

  • Do periods or illness affect ketones?

    The NHS lists being unwell, an injury or surgery, having your period and not taking enough insulin among the causes of DKA, so more frequent checks at these times are sensible.

  • Can DKA be the first sign of diabetes?

    Yes. The NHS says it can happen when people first develop type 1 diabetes and have not been diagnosed, particularly children. Call 999 or go to A&E if you have these symptoms and no diagnosis.

Where this comes from

Sources and checking.

This guide is for information, not medical advice.

Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.

Published 2026-10-10, next review 2027-10-10.

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