Headed for a routine doctor visit last year, Asha Sonawane, 63, collapsed after stepping outside her house in Bhadole village of India’s Maharashtra state as temperatures soared past 40 degrees Celsius (104 F). Her daughter Alka rushed to her with lime water and an energy drink, which relieved her a bit. But her legs hurt and she felt weak.
Dehydration in extreme heat had exacerbated Sonawane’s diabetes mellitus – a chronic medical condition in which blood glucose levels are too high – her doctor later explained.
He prescribed a few medicines and told her not to go outside for the rest of the summer.
During her long months indoors, she kept feeling dizzy despite taking the medications. Sonawane, who has had diabetes since 1997, said that even 10 years ago, she walked a lot and even worked eight or more hours a day in the field.
“I never experienced anything like this,” she said.
As heat-trapping gases cause the climate to warm, one often overlooked consequence of extreme heat is its impact on people with diabetes mellitus: 830 million people globally, 101 million of them in India.
The most common forms of diabetes are type 1 and type 2. In type 1, the immune system attacks the pancreas, producing little to no insulin. Type 2 diabetes, which is more prevalent, occurs when the body’s cells become resistant to insulin, and the pancreas cannot produce enough insulin to meet the body’s needs.
World Health Organization data shows diabetes has skyrocketed by 315% since 1990, with cases surging in low- and middle-income countries. A 2017 study indicated that rising heat may explain some of that rise, perhaps by reducing the activity of a certain kind of fat. The researchers found that a one-degree Celsius rise in temperature could cause over 100,000 new diabetes cases annually in the U.S. alone.
In 2021, more than 2 million people worldwide died from diabetes and related kidney diseases, and more than half those affected by diabetes did not take medications in 2022. Still more could suffer as global warming exacerbates the disease. One study found that in a high-emission scenario, China’s heat-related diabetes mortality could multiply eightfold by the 2090s.
In 2024, the Earth’s average temperature for the first time climbed 1.5 degrees Celsius above the preindustrial revolution level, the limit targeted by the 196 countries that signed the Paris Agreement in 2015. With that level breached, scientists warn of graver consequences as the Earth warms.
The World Meteorological Organization confirmed that 2024 was the hottest year on record, and roughly 6.8 billion people, or 78% of the world’s population, experienced extreme heat for at least 31 days that year.
Many people with diabetes may not yet be fully aware of the increased risks associated with extreme heat. Often, they manage discomfort with painkillers and continue with their daily routines throughout the summer.
But there are steps they can take. The U.S. Centers for Disease Control and Prevention offers general guidelines like drinking plenty of water, protecting medications and supplies from heat, wearing loose and light clothing, and avoiding alcohol and caffeinated beverages such as coffee, soda, and energy or sports drinks, as they can cause dehydration and raise blood sugar levels. The CDC also recommends using sunscreen and wearing a hat outdoors to protect against sun exposure.
A warming world makes diabetes deadlier
A 2022 U.S. study found that extreme outdoor temperatures, whether very high or low, increased the risk of some life-threatening conditions for people with type 2 diabetes. Those included hypoglycemia, meaning low blood sugar, and ventricular arrhythmia, a condition in which the heart beats too fast, too slow, or erratically, leading to fainting or sudden cardiac arrest.
Charles Leonard, an associate professor of epidemiology at the University of Pennsylvania, a trainee at the Yale School of Public Health, and senior author of the study, explained direct and indirect ways that rising temperatures can hurt people with type 2 diabetes.
They “can experience a blunted response to extreme ambient heat, driven by reduced skin blood flow and an impaired sweating response, such that one’s body cannot cool itself properly,” he explained. This makes heat exhaustion more likely, and the problem “can be exacerbated by some prescription medications that further impair sweating.”
Read: Common medications may increase the dangers of heat waves
He said heat also can increase the risk of swings in blood sugar levels, either very low or very high. Low blood sugar levels can lead to confusion, loss of coordination, blurry vision, slurred speech, or even seizures, while high blood sugar levels can permanently damage the eyes, blood vessels, kidneys, and nerves over the long term. Heat also makes it trickier for doctors to know how much medicine to prescribe, because of possible side effects in extreme temperatures.
Studies show more hospitalizations among people with diabetes due to extreme heat and dust. One study from Kuwait analyzed over 11,000 cases of unplanned diabetes hospitalizations between 2017 and 2019, linking hot days to an excess of 282 diabetic admissions. The study found that dust played a significant role.
“High temperatures lead to increased heat stress, which worsens glucose control and raises the risk of complications such as foot ulcers and fluctuations in blood sugar levels,” said lead author Barrak Alahmad, a population health scientist at Harvard T.H. Chan School of Public Health. “Fine dust particles also cause vascular damage and increase inflammation, further complicating the condition of people with diabetes.”
Need for more awareness
“People realize how severe this is only after their health deteriorates to the point where they can’t work in the fields anymore,” said Sonawane, who lost one of her brothers to diabetes and fears how climate change affects her health.
Leonard said people with diabetes should consult their doctors about preparing for extreme heat.
“While some preparedness examples might include identifying and seeking climate-controlled spaces, especially during the hottest part of the day, avoiding certain outdoor physical activities, staying hydrated, and checking one’s blood sugar more frequently, advice from one’s own medical provider should guide specific actions,” he said.
Climate change also threatens health care infrastructure, which affects people with diabetes and many others. Alahmad stressed that health care systems must be resilient.
“Warning systems need to be in place and targeted for vulnerable patients, including people with diabetes,” he said. “These can be built on forecasting to send warnings early enough to prompt action.” He also advocates for using and expanding telemedicine during extreme events.
Rising heat and declining health
Sonawane recalls the days when she worked 12-hour shifts in the fields. Now even a few minutes outdoors during extreme heat leaves her feeling dizzy, nauseated, and breathless. In 2019, she was forced to leave fieldwork due to her declining health and the increasing frequency of heat waves. Her 58-year-old neighbor, Gangabai Bodake, also had to quit working four years ago as rising temperatures made it harder to manage her diabetes.
“I just don’t have the energy to work as my legs hurt a lot and swell often,” Bodake said. Last summer she often experienced dizziness.
“Whenever I feel dizzy, I know something is wrong with my diabetes levels,” she explained. As a makeshift solution, she wraps her legs in a large cloth. “I know it doesn’t help much, but what else can I do?”
She also dips her legs in lukewarm water to ease the discomfort for an hour or two. When the pain becomes unbearable, she resorts to painkillers. During extreme heat, Bodake often loses sensation in her legs.
“I feel like I don’t have legs,” she said.
Bodake now gets her blood sugar levels tested every month. Her doctor has also increased her medication dosage.
“I used to take one medicine, but now I take two, and even that is not helping as my diabetes levels were way beyond the limit last month,” she said.
Being unable to work in the fields has added financial strain to her family and many others. “I can’t afford nutritious food anymore,” Bodake said.
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