At Rady Children’s Hospital in San Diego, Type 1 diabetes cases jumped almost 60% during the first year of the pandemic, compared with the previous 12 months, researchers reported recently in JAMA Pediatrics. Just 2% of those children had active COVID-19 and the report lacked information on any prior infections. But the sharp increase was striking and “clearly there’s a lot more work to be done to try to answer why is this happening,” said co-author Dr. Jane Kim.

Type 2 diabetes, which mostly affects adults, impairs how the body uses insulin, leading to poorly regulated blood sugar. Causes are uncertain but genetics, excess weight, inactivity and unhealthy eating habits play a role. It can sometimes be treated or reversed with lifestyle changes.

Globally, more than 540 million people have diabetes, including about 37 million in the United States. Most have Type 2 diabetes, and many more have higher than normal blood sugar levels, or prediabetes. Doctors worry that COVID-19 or sluggish pandemic lifestyles might be among things that push them over the edge.

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A diabetes center at Chicago’s La Rabida Children’s Hospital has seen a pandemic surge in prediabetes. Center co-director Rosemary Briars suspects long, sedentary hours of online learning played a role.

Dr. Rasa Kazlauskaite, a diabetes specialist at Chicago’s Rush University Medical Center, said steroid drugs that are sometimes used to reduce inflammation in hospitalized patients with infections including COVID-19 can cause blood sugar increases leading to diabetes. Sometimes it resolves after steroids are stopped , but not always, she said.

The physical stress of severe COVID-19 and other illnesses can also cause high blood sugar and temporary diabetes, she said.

To learn more, scientists in Denmark are enrolling adults recently diagnosed with Type 1 diabetes, including some who had COVID-19. Over time, the researchers will check whether the condition progresses faster in those who had COVID-19, which could help clarify the infection’s role, if any, in developing diabetes, said researcher Dr. Morten Bjerregaard-Andersen, a diabetes specialist at the Hospital of South West Jutland.

“The theory is if you had COVID-19, then your own insulin production will be more compromised than if you weren’t infected,” Bjerregaard-Andersen said.

Researchers at King’s College London and Monash University in Melbourne, Australia, have launched an international COVID-19-diabetes registry. Among things they hope to learn: Does diabetes in COVID-19 patients persist after they recover; do they face higher risks of getting diabetes again; could diabetes in COVID-19 patients be an entirely new type of diabetes.

Nolan Balcitis, now 12, says he knew nothing about diabetes before his diagnosis last year. He was nervous at first about all that’s involved in managing the disease — counting carbohydrates, checking blood sugar, insulin shots. But a wearable insulin pump lets him skip daily injections, and a sensor on his arm makes monitoring a breeze.

A typical kid who likes baseball and playing with his yellow Labrador retriever, Callie, Nolan shrugs off his condition.

“I’m just kind of used to it now,” the boy said with the nonchalance of an almost-teenager.