type 2 diabetes and intercurrent illness

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This guideline is not intended to serve as a protocol or standard of care:

  • this is best practice based on all clinical data available for an individual case and may be subject to change as scientific knowledge and technology advances and patterns of care evolve. Adherence to guideline recommendations will not ensure a successful outcome in every case, nor should it be construed as including all proper methods of care or excluding other acceptable methods of care aimed at the same result. Ultimately a judgement must be made by the appropriate healthcare professional(s) responsible for a particular clinical procedure or treatment plan following discussion with the patient, covering the diagnostic and treatment options available. It is advised that any significant departure from the guideline should be documented in the patient’s medical record at the time the decision is taken.

Examples of intercurrent illness where "sick day rules" would be considered (1):

The following list of such illnesses is not exhaustive:

  • the common cold
  • influenza
  • coronavirus (COVID)
  • diarrhoea and vomiting
  • urinary tract infection
  • chest infection
  • pneumonia
  • abscess
  • injury (e.g. fracture)

General advice for managing diabetes during intercurrent illness (1)

S (Sugar)

  • Blood glucose levels can rise during illness even if the person is not eating
  • Advise to increase blood glucose monitoring if the person has access to it
  • Diabetes medications (sulfonylureas and insulin doses) may need to be increased temporarily during illness to manage these raised glucose levels

I (Insulin)

  • NEVER stop insulin
  • Insulin doses may need to be increased during illness, especially if ketones are present
  • Specific advice for people on insulin therapy is presented below
  • Specific advice for people on oral diabetes medication is presented below

C (Carbohydrate)

  • Ensure the person maintains hydration and carbohydrate intake
  • If the person is not able to eat or is vomiting, advise to replace meals with sugary fluids
  • If blood glucose levels are high, maintain fluid intake with sugar-free fluids
  • If blood glucose levels are low, encourage regular intake of sugary fluids

K (Ketones)

  • In type 1 diabetes, advise to check for ketones every 2–4 hours
  • Give extra rapid-acting insulin doses (in addition to regular doses) based on total daily
  • insulin dose if ketones are present – see insulin algorithm below
  • Advise to drink plenty of water to maintain hydration and flush through ketones

With respect to diabetic medications (5):

With respect to non-diabetic medications (5):

For those patients taking sulphonylurea medication:

  • patients taking this medication should have access to blood glucose monitoring equipment; frequency of self-monitoring of blood glucose (SMBG) should be increased to a minimum of daily - with a range of fasting and pre-meals (especially if dietary intake is affected)
  • appropriate advice should be provided regarding the increased risk of hypoglycaemia - usually more likely in the early stages of illness, especially if reduced dietary intake is a factor i.e. reinforce the importance of taking some form of regular carbohydrate
  • the patient should be advised to contact their health care professional if glucose level increases beyond 17 mmol/L and/or the patient feels unwell, medical advice should be sought (2)

For those taking insulin therapy:

Encourage adequate dietary and fluid intake:

    • Advice is similar to that for Type 2 Diabetes treated with oral sulphonylurea medication, with greater emphasis again on the importance of regular carbohydrate intake and options for lighter carbohydrate foodstuffs (especially at usual mealtimes/when insulin is administered)

Increase frequency of blood glucose monitoring/advice re insulin therapy:

    • Frequency of SMBG should be increased to a minimum of twice a day - with a range of fasting and pre-meal testing (especially if dietary intake is affected)
    • INSULIN SHOULD NEVER BE OMITTED, despite a reduction in dietary intake; often both patients and carers have to be convinced that this is the appropriate course of action
    • Increased insulin requirements are often required during periods of illness and ill-health; the patient should be advised to contact their healthcare professional if blood glucose levels are persistently > 25 mmols/mol (3)
    • It is appropriate to provide the patient with a simple and individualised plan for adjusting insulin based on blood glucose results

Admission or specialist advice in type 2 diabetes (3,4)

The decision to admit a person or seek specialist advice will depend on clinical judgement, taking into account the person's age, underlying comorbidities and complications, and the presence of hyperglycaemia and ketosis.

  • immediate hospital admission is indicated if:
    • is an immediate risk of diabetic ketoacidosis (DKA)
    • blood glucose persistently >20 mmol/L despite best therapy (3)
    • there is moderate ketonuria (2+ on urine dipstick) or ketonaemia (1.5–2.9 mmol/L) with or without hyperglycaemia and the person cannot eat or drink, as there is a risk of DKA
    • a person treated with insulin does not improve rapidly with insulin treatment (4)

  • consider arranging hospital admission or seeking urgent specialist advice if (4):
    • underlying condition is unclear
    • person is dehydrated or at risk of dehydration
    • vomiting persists beyond 2 hours.
    • person and their family/carers are unable to keep the blood glucose level above 3.5 mmol/L.
    • person and their family/carers are exhausted, for example due to repeated night-time waking.


  • Down S. How to advise on sick day rules. Diabetes & Primary Care (2018); 20 (1): 15-16.
  • NHS London Clinical Networks. Sick day rules: how to manage Type 2 diabetes if you become unwell with coronavirus and what to do with your medication (Accessed 8/5/2020)
  • Patient.co.uk (Accessed 8/5/2020).Diabetes and Intercurrent Illness.
  • CKS (Accessed 8/5/2020). Type 2 Diabetes.
  • NHS Sandwell and West Birmingham CCG (Accessed 23/9/2020). Sick day rules: how to manage Type 2 diabetes if you become unwell with
  • coronavirus and what to do with your medication

Last edited 10/2020 and last reviewed 12/2020