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Hyperglycemia & the Link Between Diabetes and COVID-19 Deaths

Feb 27, 2021
Editor: Steve Freed, R.PH., CDE

Author: Leyany Feijoo Ramos, PharmD. Candidate, LECOM School of Pharmacy

COVID-19 and hyperglycemia: even patients without diabetes may be at a higher risk for complications and mortality if their blood glucose is elevated. 

Several chronic conditions have been associated with a higher risk of severe illness with COVID-19, including CKD, COPD, obesity, compromised immune system, several heart conditions, sickle cell disease, and T2DPrevious studies have indicated that hyperglycemia increases mortality risk in community-acquired pneumonia, acute MI, severe SARS, and MERS (which are also coronaviruses), among others. However, the effect of fasting blood glucose (FBG) on outcomes in COVID-19 patients has not been fully described. Even though vaccines and several treatment strategies are being studied, research to further identify patients at higher risk for complications is imperative due to the high number of cases. 


A study conducted in Wuhan, China, evaluated how FBG levels upon admission affected mortality risk and complications in patients without diabetes who had COVID-19. Researchers conducted a two-center retrospective study that included 605 patients with a definitive outcome within 28 days between Jan. 24 and Feb. 10. A definitive outcome was defined as death, hospital discharge, or current hospitalization. Fasting blood glucose levels were collected within 24 hours of admission after an overnight fasting period of at least 8 hours. Only those who had this level available were included in the analysis. Patients were assigned to groups based on their FBG upon admission; 329 patients had a level of <6.1 mmol/L, 100 patients had 6.1-6.9 mmol/L, and 176 patients had seven mmol/L. Researchers assessed the severity of COVID-19 using CRB-65 scores since all study participants had pneumonia, often seen in hospitalized COVID-19 patients. Participants were divided into groups based on a score of 0 (mild, n= 334), 1 to 2 (moderate, n=261), or 3 to 4 (severe, n=10).  

Patients included in the study had a median age of 59, a higher number were men than women (53.2% versus 46.8%), and 208 (34.4%) had a past medical condition. Out of the 605 patients included, 114 died within 28 days of being hospitalized, which accounted for 18.8% of study participants. After analysis, non-survivors were found to be older (p<0.0001), male (p=0.0003), and with a past medical condition (p=0.0005), including cerebrovascular disease (p=0.0098). Additionally, a higher percentage of patients who did not survive had CRB-65 scores of 3 to 4 (6.1%) and FBG of  7 mmol/L (50.9%) compared to those who survived (0.6% and 24%, respectively). On the other hand, a higher percentage of survivors had FBG upon admission of <6.1 mmol/L (59.9%).  

Factors such as age (HR 1.02), male sex (HR 1.75), a CRB-65 score of 1 to 2 (HR 2.68), a CRB-65 score of 3 to 4 (HR 5.25), and FBG of  7 mmol/L (HR 2.30) were found to increase the risk of mortality independently. Additional analysis showed that mortality risk increased as blood glucose increased. Participants with FBG between 6.1 and 6.9 mmol/L (HR 2.06) and those with FBG 7 mmol/L (HR 3.54) had a higher risk of death than those with lower blood glucose levels. Additionally, compared to those with FBG between 6.1 and 6.9 mmol/L, participants with a fasting level of 7 mmol/L or higher (HR 1.72) had a higher risk of death. Similarly, mortality risk was also higher as CRB-65 scores increased, and those with a score of 3 to 4 had the highest chances of death. However, regardless of CRB-65 scores, FBG levels of 7 mmol/L or more were associated with increased mortality. Complication rates were also higher among those with higher fasting blood glucose levels. Compared to those with lower FBG levels, participants with FBG of  7 mmol/L and 6.1 to 6.9 mmol/L upon admission increased risk for complications (OR 3.99 and 2.61, respectively).   

This study had several limitations, including its retrospective design. They did not evaluate how different therapies used to lower blood glucose affected mortality or complications in these patients. However, these results suggest closer glucose monitoring and control, even in patients without diabetes, may positively affect outcomes in COVID-19 patients. Additionally, tighter glucose control in patients with diabetes is also needed since this could reduce complications in these patients. Future studies should evaluate how different medications used to lower blood glucose in patients with COVID-19 and hyperglycemia upon admission affect mortality risk. 

Practice Pearls: 

  • FBG levels of 7 mmol/L or higher at admission independently increased the risk of mortality and complications in COVID-19 patients without diabetes.  
  • COVID-19 mortality risk and complications increased as the level of hyperglycemia increased, regardless of CRB-65 scores. 
  • Closely monitoring for hyperglycemia and controlling glucose levels in all patients with COVID-19 could significantly improve outcomes. 


Wang, S et al. Fasting blood glucose at admission is an independent predictor for 28-day mortality in patients with COVID-19 without previous diagnosis of diabetes: a multi-center retrospective study. Diabetologia (2020).   

“Cases in the US” Centers for Disease Control and Prevention, July 2020. 

“People Who Are at Higher Risk for Severe Illness.” Centers for Disease Control and Prevention, July 2020. 


Leyany Feijoo Ramos, PharmD Candidate, LECOM School of Pharmacy