COVID-19 and diabetes – Why people with diabetes are more susceptible to severe illness from COVID-19 and how to prevent it?

By Dr Alexia Alexandraki*

Coronavirus-Disease 2019 (COVID-19) is a virally infectious disease caused by the novel coronavirus called “Severe Acute Respiratory Syndrome Coronavirus-2” also known as SARS-CoV-2, initially emerged in Wuhan, China, on December 2019. On the 30th of January 2020, COVID-19 was declared the sixth public health emergency of international concern by the World Health Organization (WHO)1.

The virus is transmitted via human-to-human interactions that can be mediated through inhalation of infective respiratory droplets occurring during coughing or sneezing, direct contact with an infected individual (i.e shaking hands) or by touching contaminated surfaces2,3. The symptoms most commonly include fever, sore throat, cough, difficulty in breathing, myalgia, fatigue. Symptoms can be mild in the majority of the cases (80%) but can also be severe usually in the elderly and in the susceptible population resulting in pneumonia, acute respiratory distress syndrome (ARDS) and multi-organ dysfunction. At the same time some people may be asymptomatic4,5.

Populations, who are at a greater risk developing severe illness from COVID-19 include older individuals and people of any age with underlying medical conditions including people with moderate to severe asthma, people with human immunodeficient virus (HIV), people with chronic lung disease, serious heart conditions, chronic kidney disease, liver disease and diabetes (Centers for Disease Control and Prevention – CDC)6. This article will briefly explain why people with diabetes are more susceptible to develop severe illness upon infection with SARS-CoV-2 (COVID-19) and what are the protective precautions that can be applied against it.

Diabetes is one of the leading causative agents of morbidity and mortality with a total of 463 million diabetic individuals worldwide and 4.6 million deaths being reported in 2019 according to the International Diabetes Federation7. According to the American Diabetes Association, individuals with diabetes are more susceptible in developing serious complications from COVID-198, which may include bacterial pneumonia9. Diabetes mellitus also known as diabetes, is characterised by chronic hyperglycaemia (excess blood glucose) due to insulin deficiency or insulin resistance resulting in metabolic disturbances. There are two main types of diabetes including Type 1 diabetes (lack of insulin) and the most commonly diagnosed Type 2 diabetes (insulin deficiency and/or insulin resistance)10.

Reasons that can explain why individuals with diabetes are at higher risk of developing severe forms of illness from COVID-19 include the following:

  • Individuals with diabetes have an impaired immune response to infections that may involve lower secretion of inflammatory cytokines, reduced response of T-cells and impaired neutrophil function11,12.
  • Abdominal obesity in diabetic individuals has been associated with abnormal secretion of adipokines, chemokines and inflammatory cytokines such as the Tumour Necrosis Factor alpha (TNF-alpha), leading to chronic low-grade inflammation in adipose tissue9,11. Maintaining chronic, low-grade inflammation in the body may induce impaired immune-response to infections11,13.
  • Individuals with abdominal obesity tend to develop mechanical respiratory problems such as obstructive sleep apnea, obesity hypoventilation syndrome, exertional dyspnea and chronic obstructive pulmonary disease14,15,16.
  • Obese population have higher risk in developing asthma16,17.
  • Chronic diabetic complications such as nephropathy and cardiovascular diseases may complicate the situation of individuals with diabetes by increasing severity of COVID-19 disease18.
  • Hypertension and diabetes are often treated with angiotensin-converting enzymes (ACE) inhibitors. Evidence suggest that use of ACE inhibitors may both benefit or cause harm in the context of the COVID-19 pandemic19,20. Advice on the use of ACE inhibitors is under review. Changing routine drug consumption should be avoided without approval from your expert clinician.
  • Complications that may be associated with viral infections such as SARS-CoV-2 in individuals with diabetes include:

Diabetic ketoacidosis – A life-threatening medical emergency triggered by elevated blood glucose levels that cannot be regulated due to insulin deficiency resulting in impaired glucose distribution to the peripheral tissues21. Increased glucose levels can be stimulated in response to stress, infectious diseases, acute illness or use of certain drugs22. The body then begins to break down fatty acids causing release of fatty acids in the circulation, which are then converted into ketones in the liver, as an alternative source of energy. There are three main ketone bodies: acetone, acetoacetate and β-hydroxybutyrate. Dissociation of excess ketone bodies results in generation of a large load of hydrogen ions causing the blood to become more acidic (drop in pH) resulting in ketoacidosis that requires medical attention22,23.

Pneumonia – Cohort studies indicated that individuals with diabetes are at a higher risk for pneumonia-related hospitalization compared to nondiabetic individuals24-26. The risk for hospitalization with pneumonia increases in diabetic individuals practising poor long-term glycemic control24. Susceptibility to pneumonia in individuals with diabetes can be attributed to hyperglycemia, decreased immunity and chronic complications such as impaired lung function24-28.

Dehydration – People with diabetes are at a higher risk of dehydration due to the high levels of blood glucose. Glucose is an osmotically active substance that attracts water towards it. In hyperglycaemia, glucose levels are higher in the blood and low in the cells resulting in cellular dehydration10,29. If diabetic individuals experience COVID-19 related symptoms such as fever and/or diarrhea, these patients may be more susceptible to dehydration, especially when good body hydration is not maintained. Achieving ideal glucose blood levels, ensuring sufficient fluid intake and controlling electrolyte levels are advised in order to maintain good hydration in the body and to reduce the risk of severe complications especially in the case of viral infections such as COVID-19.


  • Practise more frequent blood glucose monitoring (if self-monitoring is applied)30.
  • CDC and others advice people with diabetes to take influenza and pneumonia vaccinations for best protection against serious complications in response to such medical conditions31.
  • Self-management of diabetes during the COVID-19 pandemic including checking feet daily, maintaining a healthy diet and physical activity30.
  • Acute exercise bouts enhance the activity of T-lymphocytes, a type of leucocyte that possesses a major role in the immune defense mechanisms. Exercise can also lower the levels of stress hormones such as cortisol and adrenaline32.
  • Enhance the immune system by getting at least 7 hours of sleep, reducing stress levels, ensuring adequate intake of food and fluids.

*Despite the fact that people with diabetes are at higher risk of severe complications from COVID-19, it is possible to reduce the risk by maintaining physiological glucose levels in the blood and by applying the prevention measures against COVID-19.

*Dr Alexia Alexandraki
Post-Doctoral Scientist
Department of Biological Sciences
University of Cyprus
Member of the 77 board of “New Wave – The Other Cyprus”