People with diabetes are at greater risk of infection and serious complications as a result in comparison to the general population (Diabetes Care, 2018).

Similarly, illnesses and infections affect the blood glucose levels often causing the levels to rise and make their condition worse. Thus it is important for the person with diabetes to recognise the signs and symptoms of underlying illness and seek prompt advice from their GP or local pharmacist to manage this.

Healthcare professionals and others involved need to know what to do and how to monitor blood glucose levels to keep the diabetes under control. Extra insulin is sometimes necessary, so healthcare professionals and people with diabetes need to know how to manage the ‘sick day rules’.

Blood glucose levels may rise even where people are not eating their normal food or drink.

If unsure, always refer to the Diabetes Specialist for advice or seek urgent medical help:

• if the healthcare professional and/or person with diabetes is not sure what to do
• if the person with diabetes is persistently vomiting (not able to hold down any food or drink for more than six hours), they can quickly become very dehydrated
• if blood glucose levels remain high or ketone levels continue to rise despite interventions.

Type 1 diabetes

Key points

• insulin should never be stopped
• insulin doses may need to be increased and/or additional doses of fast acting/rapid insulin may be necessary to bring down blood sugars levels. A Diabetes Specialist will be able to prescribe an insulin adjustment table
• blood glucose levels should be checked at least every two to four hours
• encourage the person to drink clear sugar free fluids to avoid dehydration
• food can be taken in alternative forms, for example sugary drinks, boiled sweets, or glucose tablets.

What should be the aim for blood glucose levels when a person with diabetes is ill?

Aim: Blood glucose target between 6-10mmol/L

Testing 

• if the blood glucose levels stay above 10mmol/L follow the individual prescribed guideline by the Diabetes Specialist for increasing their insulin dose
• extra blood glucose testing will be necessary. Glucose levels will need to be tested every two to four hours and every two hours if blood glucose levels remain high.

Ketones

• everyone with type 1 diabetes should have urine ketone testing strips or a ketone meter at home to check high blood glucose levels
• healthcare professionals working in a hospital ward will be able to perform a simple urine test or use a blood ketone meter to test ketone levels
• moderate to high urine or blood ketones levels will usually indicate that blood glucose levels are high and extra insulin is needed.

Ketoacidosis - also known as Diabetic ketoacidosis (DKA)

People with diabetes need the correct amount of insulin in their body at all times. The extra demands of illness mean their need for insulin will increase, even if they are not able to eat. If there is not enough glucose getting into the cells of the body, fat stores are used as an alternative source of energy.

Because the body can’t burn up fat very efficiently, by-products known as ketones are given off. Ketones are acids and therefore make the blood “acidic”. Not getting enough insulin at this time and if it is left untreated can result in ketoacidosis, and the person with diabetes may become seriously unwell. If the person doesn’t respond to treatment at home within six hours they may need to be treated in hospital.

Symptoms of ketoacidosis include:

• blood glucose over 15 mmol/L
• ketones in your urine or/and blood
• thirst
• passing large amounts of urine (this leads to dehydration)
• tiredness
• abdominal pain.

A person with diabetes should seek urgent help if they have the following symptoms:

• vomiting
• rapid breathing
• reduced level of consciousness (drowsiness).

When the person has recovered from their illness and their blood glucose levels are back to normal, It is important to remember to reduce the insulin dose back to the usual dose to prevent hypoglycaemia.

Type 2 Diabetes

When blood glucose levels are high a person will usually experience the following symptoms:

• thirst/dry mouth
• passing large amounts or urine (this can lead to dehydration)
• tiredness
• weight loss.

Type 2 Diabetes on tablets

People with type 2 diabetes on tablets should keep taking their medication unless advised otherwise.

Metformin or/and SGLT2 or/and GLP-1 and GLP-1/GIP only

If a person has a severe infection or is becoming dehydrated they need to temporarily stop taking Metformin or/and SGLT2 tablets or/and GLP-1 and GLP-1/GIP. They should seek advice from their GP or Diabetes Specialist team. They may need a different treatment for their diabetes until they can re-start their Metformin tablets.

Metformin or/and Sulphonylurea

The most commonly used Sulphonylurea tablets are called Gliclazide. Sulonylurea tablets can cause the blood glucose to fall too low. A person with diabetes may have been provided with blood glucose testing equipment to check if their blood glucose has fallen too low, i.e. hypoglycaemia. Recommend delete or clarify They will need to routinely monitor their diabetes. Blood glucose levels can also be checked once in hospital. If the person is ill their blood glucose levels will usually rise. In this instance blood glucose levels will need to be tested more frequently, at least two to four times per day.

Their medication may need to be temporarily increased to control blood glucose levels until they are better.

Type 2 Diabetes and Insulin

People with Type 2 diabetes on insulin must:

• be provided with equipment to test their own blood glucose levels at home or/and once in the hospital
• aim to keep their blood glucose levels between 6 and 12mmol/L
• If their glucose levels remain above 12mmol/L when they are ill, they must follow advice on increasing insulin doses from the Diabetes Specialist
• extra blood glucose testing will be necessary. Glucose levels will need to be tested every four hours especially if blood glucose levels are high (over 14mmol/L).

Ketones

If the persons blood glucose gets too high, (over 14mmol/L) they may need a urine test for ketones, (hospital policies may vary). People with Type 2 diabetes are not routinely prescribed urine ketone testing strips to test for ketones themselves at home.

Insulin and tablets

If a person with type 2 diabetes has a severe infection or is becoming dehydrated they may need to stop taking Metformin tablets or/and SGLT2 or/and GLP-1 alongside the insulin. They should continue taking the insulin and urgently seek medical advice from the GP or/and Diabetes Specialist team or/and call 111. 

If the person is taking a Sulphonylurea tablet (Gliclazide) they should either continue their normal dose, or increase the dose as advised by the Diabetes Specialist team.

The maximum dose of tablets is:

• Metformin 500mg, two tablets (1 gram) twice daily 
• Gliclazide 80mg, two tablets (160 mg) twice daily.

Managing insulin doses during illness for Type 2 diabetes

• monitor and record blood glucose levels at least four times a day ( at mealtimes event if not eating and at bed time)
• if blood glucose levels are consistently higher than 14mmol/l the insulin doses may need to be increase, seek immediate advice from the Diabetes Specialist Team/GP.

Further resources

• ABCD - How to manage Type 1 Diabetes during illness – If you are on an insulin pump
• Carey, M et al (2018) Risk of Infection in Type 1 and Type 2 Diabetes Compared With the General Population: A Matched Cohort Study, Diabetes Care, 2018, 41(3): 513-521
• NHS England (2020) Sick day rules for patients on multiple daily injections (MDI): how to manage type 1 diabetes if you become unwell with coronavirus

Guidance for patients

• Diabetes UK. Diabetes when you're unwell
• Breakthrough T1D. Managing sick days. Sickness and Type 1 diabetes
• TREND. Type 1 diabetes - what to do when you are unwell

COVID‑19 continues to pose a significant health risk for people living with diabetes, even as we move into a phase where the virus is managed in a way more comparable to seasonal flu. While the acute emergency response has evolved, the evidence remains clear: individuals with diabetes are more likely to experience severe illness, complications and prolonged recovery if they contract COVID‑19.

This makes ongoing vigilance, vaccination, and proactive risk‑factor management essential parts of routine care. In current practice, our focus has shifted from crisis response to sustainable, long‑term management—much like our approach to influenza. This includes promoting vaccination, supporting people to maintain stable glucose levels, recognising early signs of deterioration, and ensuring rapid access to treatment when needed.

By embedding COVID‑19 considerations into everyday diabetes care, nurses can continue to protect those at higher risk while maintaining a balanced, practical approach that aligns with wider public health strategies.

What do we know about COVID-19 

• coronaviruses are a large family of viruses which may cause illness in animals or humans
• there are many types of human coronaviruses including some that commonly cause mild upper-respiratory tract illnesses
• COVID-19 (CoronaVIrus Disease - 2019) is caused by a novel (or new) coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
• SARS-CoV-2 is the seventh coronavirus known to infect humans.

Groups with a greater risk include:

• people age over 70 and older
• people who live in nursing homes.

Other high-risk conditions could include:

• people of any age with severe obesity (BMI >40 kg/m2) or certain underlying medical conditions, particularly if not well controlled, such as those with diabetes, renal failure, or liver disease might also be at risk
• people with chronic lung disease or moderate to severe asthma
• people who have serious heart conditions
• people who are immunocompromised including cancer treatment
• pregnant women should be monitored since they are known to be at risk with severe viral illness.

Some facts about COVID-19 and diabetes

1. people with diabetes are not more likely to get COVID-19 than the general population
2. diabetes is one of the high-risk groups for developing severe illness from COVID-19
3. people with type 1 diabetes have an increased risk of developing diabetic ketoacidosis if infected with viral or bacterial infections
4. the risk of mortality remains low under the age of 40
5. the death rates of people with diabetes doubled during the early phase of the pandemic
6. people with T1D and T2D, men, BAME ethnicity or living in more deprived circumstances are at a higher risk of mortality
7. tight glycaemic control and low BMI are also risk factors of mortality with COVID-19
8. in both T1D and T2D, those with pre-existing kidney disease, heart failure and previous stroke are at a higher risk of mortality
9. hyperglycaemia and obesity are linked to increased risk of mortality.

Management of people with diabetes infected with COVID-19

• patients should follow the advice of the GP or/and Diabetes Specialist Team on adjustments to their anti-diabetic medication(s)
• blood glucose levels should be frequently checked (generally, every 2-4 hours, keeping records)
• management of COVID-19 infection by patient and HCPs should follow diabetes sick day rules appropriate to any other infections
• patients should be aware of signs and symptoms of hyperglycaemia.  

Therapeutic aims (follow your local guideline)

• plasma glucose concentration: 4-8 mmol/L
• HbA1c < less than 53 mmol/mol (7%)
• CGM/FGM targets of 4-10 mmol/L
• preventing Hypoglycaemia <3.9 mmol/L.

Consideration of potential metabolically interfering effects of drugs in suspected or COVID-19 positive patients with type 2 diabetes

Metformin

• dehydration and lactic acidosis will probably occur if patients are dehydrated, so patients should stop taking the drug and follow sick day rules
• during illness, renal function should be carefully monitored because of the high risk of chronic kidney disease or acute kidney injury.

Sodium-glucose co-transporter 2 inhibitors (SGLT-2)

• risk of dehydration and diabetic ketoacidosis during illness, so patients should stop taking the drugs and follow sick day rules
• patients should avoid initiating therapy during respiratory illness
• renal function should be carefully monitored for acute kidney injury. 

Insulin

• insulin therapy should not be stopped
• regular self-monitoring of blood-glucose ever 2-4 hours should be encouraged, or continuous glucose monitoring
• carefully adjust regular therapy if appropriate to reach therapeutic goals according to diabetes type, comorbidities, and health status.

Glucagon-like peptide-1 receptor agonists (GLP-1)

• dehydration is likely to lead to a serious illness so patients should be closely monitored
• adequate fluid intake and regular meals should be encouraged.

Dipeptidyl peptidase-4 inhibitors (DPP4)

• these drugs are generally well tolerated and can be continued. 

People with diabetes should have ready

• contact information of health care provider
• a stock of medications and supplies for monitoring blood glucose
• enough stock of simple carbohydrates like regular soda, honey, jam, etc. to manage low blood glucose
• glucagon, blood and/or urine ketone strips.

Summary

• diabetes is a frequent comorbidity in COVID-19 patients
• practical recommendations are emerging to help with clinical management and many national and international bodies are continually updating their guidance
• more data is needed to better define the nature of interaction between diabetes and COVID-19
• research into potential therapies along with a preventative vaccine is urgently needed
• COVID‑19 should continue to be regarded as a serious health risk for people living with diabetes, but it now sits alongside other seasonal illnesses such as flu, where nursing staff play a vital role in supporting safe, proactive and person‑centred care.

Further resources

• Association of British Clinical Diabetologists (ABCD) Coronavirus
• Diabetes on the net (DOTN) COVID-19 resources
• Diabetes UK. Advice for healthcare professionals on COVID-19 and diabetes