COVID-19: Why Blood Sugar Matters


The more we learn about COVID-19, the more we learn how critical blood sugar management is.

In late April, the prestigious medical journal The Lancet published this eye-opening statement:

People with diabetes who have not yet been infected with the SARS-CoV-2 virus should intensify their metabolic control as needed as means of primary prevention of COVID-19 disease. 

This advice (PDF) was authored by an international constellation of endocrinologists in an attempt to produce a swift medical consensus on this issue of pressing need. The expert directive confirms what many have suspected now for months: that blood sugar management is critically important to people with diabetes under the threat of the novel coronavirus, and that tight glucose control should be prioritized as a primary means of defense against the disease that the coronavirus causes.

We are concerned that the diabetes authorities that most of us look to have been slow to broadcast this message. The American Diabetes Association notes that poorly managed diabetes is associated with increased risks due to the accumulation of long-term damage, but doesn’t say a word about glycemic control in its “Take Precautions” page., a collaboration between JDRF and Beyond Type 1, only hints at the importance of glycemic control. That website advises to “test blood sugars more often” and to “maintain blood sugar friendly eating,” without any indication that healthy blood sugars may be of newly vital importance during the pandemic.

In the meantime, the evidence continues to pile up. On April 30, a study published in Cell Metabolism found a truly stark difference in outcomes between patients with “well-controlled” blood glucose and “poorly controlled” blood glucose.

The numbers, actually, are shocking. Patients with type 2 diabetes that were unable to keep their blood sugar under 180 mg/dL (10 mmol/L) two hours after meals were literally 10 times as likely to die: “in-hospital death rate was significantly lower (1.1% versus 11.0%) in the well-controlled group relative to the poorly controlled group.” Patients with poorly controlled blood glucose were also significantly more likely to suffer other major complications from COVID-19, including acute respiratory distress syndrome, heart and kidney injuries.

(A note for our readers with type 1 diabetes: it would be foolish to put too much stock into the specifics of a study of patients with type 2 diabetes, a different condition that presumably has different interactions with COVID-19. Nevertheless, the study could fairly be interpreted as generally adding to the preponderance of evidence that yes, when it comes to the coronavirus, blood sugar matters.)

This is not the first study to conclude that glucose management is crucial, but the results are perhaps so dramatic that they may prompt some skepticism. Does a high blood sugar actually cause dangerous outcomes, and would lowering the blood sugar of these COVID-19 patients (through insulin, diet, or other medicines) quickly and meaningfully improve their health? Or is the high blood sugar merely an indication of poorer health in general, or the side effect of an illness that doctors don’t know yet how to combat (correlation without causation)?

It’s difficult to say, but there is plenty of evidence that lends credence to the results. For one thing, the two patient groups (well-controlled and poorly controlled) were otherwise well-matched. They were the same age, roughly the same weight, had the same incidence of other co-morbidities, and CT scans confirmed that they had similar lung health; there is no evidence that one group was simply healthier than the other. Importantly, the well-controlled glucose patients also exhibited significantly superior glucose control prior to illness, as measured by A1c (6.1% vs 7.9%). This a very strong indication that blood sugar control prior to infection was highly meaningful in the progress of the disease.

Good glucose control is important, and what’s more, it is achievable, and should therefore be stressed in every official recommendation to people with diabetes.

Notify of
oldest most voted
Inline Feedbacks
View all comments
3 years ago

Another excellent article on how each of us can impact and lower our risk of contracting a virus – even one this challenging. Thanks for being an important voice in the wilderness for diabetics. Let this be known far and wide. I will share this with my friends. Thank you.

PS – I would love to see an article on vitamins that can enhance our immunity. TIA!

Sean Dolan
Sean Dolan
3 years ago

Good summation. Thanks! I read the Cell Metabolism study but was unsure about whether the A1c cited was just an estimate of short-term control after admission or included how well glucose was managed in the 2-3 months prior to sickness (since the authors noted that they did not have access to patients’ prior medical records). Good to know that strict glucose control prior to infection can have a prophylactic effect on the course of the disease, since the big unanswered question was whether someone could have good control prior to being sick but have their body react poorly and have… Read more »

Copyright © 2009-2021 Diabetes Media Foundation, All Rights Reserved.
ASweetLife™ is a trademark of the Diabetes Media Foundation, All Rights Reserved.
Would love your thoughts, please comment.x