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Infectious Diseases

Updated 24 July 2020

High blood sugar in Covid-19 patients who have never had diabetes can cause death

New research from China shows that abnormally high blood sugar in Covid-19 patients is associated with more than double the risk of death, and increased risk of complications.

  • A link between diabetes and the potential for severe Covid-19 had already been established
  • But researchers looked at Covid-19 patients with high glucose levels - and never had diabetes
  • Those with an elevated fasting blood glucose level faced poorer outcomes


As Covid-19 continues to cause devastation around the world, researchers are making new discoveries every day, showing how the virus is causing severe sickness and death in many people.

Now, new research from Wuhan, China, shows that abnormally high blood sugar in Covid-19 patients is associated with more than double the risk of death and increased risk of complications – but the scary thing is that these high blood sugar levels occurred in Covid-19 patients without previous diabetes.

This study was published in Diabetologia, the journal of the European Association for the Study of Diabetes (EASD).

Diabetes, hyperglycaemia and Covid-19

We now know that there is an established link between diabetes and increased mortality in Covid-19, especially in South Africa, where diabetes seems to be the most prevalent co-morbidity in those who die from Covid-19.

However, the aim of this study was to determine the correlation between high fasting blood glucose and the clinical outcome for Covid-19 who were not previously diagnosed with diabetes.

In this retrospective study, 605 Covid-19 patients were observed in two hospitals in Wuhan, China, over a 28 day period. A total of 34% of the patients had underlying conditions such as hypertension, but none were previously diagnosed with diabetes.

But, at admission, 29% of the patients had a high fasting blood glucose result of 7.0 mmol/L, which would indicate type 2 diabetes if measured consecutively over time. A further 17% were in the range that would be considered pre-diabetic (6.1-6.9 mmol/L). Just more than half (54%) were, however, in the "normal" FBG (fasting blood glucose) range of 6.0 mmol/L or below, according to the news release.

The patients in the higher FBG group were 2.3 times more likely to succumb to Covid-19, and those with pre-diabetic measures were 71% more likely to die than those at the normal or lower levels.

The authors said: "This study shows, for the first time, that elevated FBG (7.0 mmol/l) at admission is independently associated with increased 28-day mortality and percentages of in-hospital complications in Covid-19 patients without previous diagnosis of diabetes... we have also shown that FBG of 7.0 mmol/l or higher is associated with increased mortality, regardless of whether the patient has pneumonia that is more or less severe."

"These results indicate that our study included both undiagnosed diabetic patients and non-diabetic patients with hyperglycaemia caused by an acute blood-glucose disorder, since the 29% found in the highest FBG group is much higher than the estimated prevalence of diabetes in the Chinese population at 12%. Similar to what was found in a previous study, Covid-19 patients might suffer from high blood sugar brought about by other conditions, and critically ill patients may develop acute insulin resistance, manifested by high levels of blood sugar and insulin levels. Patients with conditions not related to diabetes, such as severe sepsis, systemic inflammatory response syndrome (SIRS) and traumatic brain injury tend to have abnormally high blood sugar," they stated in the news release.

Study limitations

The researchers stated that there are several limitations, including the fact that it was a retrospective study and that glycated haemoglobin (HbA1C), a long-term indicator of blood sugar control issues, was not investigated.

They do believe acute hyperglycaemia plays a bigger role than long-term glycaemic control issues in predicting the outcome of Covid-19 patients.

READ | Covid-19: Experts worry that the virus is triggering diabetes in otherwise healthy people

READ | Blood sugar control for diabetics more vital than ever during coronavirus pandemic 

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