Extreme Heat Imperils Chronic Disease Patients In Informal Settlements Lack of ventilation, cooling methods and increased susceptibility to heat makes every summer dangerous for those living with chronic disease in India’s urban slums and settlements Hemanth Chandu, Pavani Pendyala Vijayawada and Guntur, Andhra Pradesh: Within hours of sunrise, the two-room flats in the government-constructed apartment in New Rajarajeshwari Peta in Vijayawada feels like a pot on a stove. By 11 a.m., Vidya (name changed) sits outside her home with her neighbours under the shade of a tree. The women chat and laugh, relieved to escape the summer heat inside the house. Vidya who is in her late 30s lives on the ground floor or a four-storey building, in a resettlement colony constructed more than a decade ago for low income families. “Ee vadagaalpula valla intlo baaga aaviri vachesthundi. With these hot winds, heat builds up in the house like steam. I find it difficult to breathe sometimes,” she said. But for Vidya, it is more than just physical discomfort. She is diabetic and feels her condition worsen during the summer. Extreme heat is known to exacerbate health risks of those living with chronic diseases. About 57% of Indian districts, home to 76% of the country’s population, are at high to very high heat risk, a 2025 study by Council on Energy, Environment and Water (CEEW) showed. Andhra Pradesh is among the most heat-prone states. A study done by the India Meteorological Department’s scientists published this year shows that the average maximum temperature across India increased by ~0.5°C by 2000, and by ~1.0°C by 2020. Northwestern and central India and the coast of Andhra Pradesh experienced the most significant increase. Between 1981 and 2000, these regions experienced an average of 2.5 to 5.5 heatwave days per year. However, over the two decades between 2001-2020, the frequency of heatwaves has increased with 3.5-8.5 days per year, particularly in northern, western, south-central, central-east, and peninsular India. IMD has forecast heatwave to severe heatwave conditions in 17 states and Union territories, including parts of Andhra Pradesh such as Vijayawada and Guntur. ISignal reached out to the Union and state health ministries for comment. We will update this story when we receive a response. How heat affects those with comorbidities “The body’s homeostatic mechanism, meaning how we adapt to any change in our external environment, such as high heat, becomes impaired in those with chronic diseases like hypertension, diabetes, renal disease, among others,” said Vivekanand Jha, executive director at The George Institute for Global Health, India, and a nephrologist and public health researcher. For blood pressure patients, excessive sweating can lead to a drop in blood pressure. “We have seen in clinics that people with well-controlled hypertension suddenly experience low blood pressure during extreme heat. They become giddy and weak. And when we measure their blood pressure, it is low. So, during the summer months, we have to reduce the number of blood pressure medicines, especially diuretics, which increase the urine flow, increasing loss of fluid,” Jha added. Diabetics are at greater risk for heat-related illnesses because of their impaired capacity to dissipate heat, and this can have important consequences on cardiovascular regulation and glycemic control. For insulin-dependent diabetics, during extreme heat, the body is unable to absorb insulin, resulting in uncontrolled sugar levels. “Insulin needs refrigeration at 4 degrees Celsius. Many in informal settlements don’t have access to a fridge, so obviously they don’t have access to effective insulin.,” Jha explained. In renal disease, the loss of salt and water due to excess heat can result in loss of kidney function. “Let’s say a manual worker goes out to work in extreme heat from morning to evening,” he continued. “By evening, their kidney function becomes lower than normal. The kidney function may recover after the worker returns home and has water for the day, but repeated insults to the organ can result in long-term injury, resulting in chronic kidney disease which can progress to kidney failure.” Gig and platform workers without access to toilets avoid drinking water, which ends up impacting their kidneys, as ISignal reported in April 2026. Extreme weather can also trigger hospital visits and mortality risk as the body struggles to regulate itself under heat stress. For Vidya and other residents of informal settlements, who are already more vulnerable to the effects of climate change, the additional burden of having a chronic health condition poses further risk. Mounting health problems A couple years ago, Vidya used to run a food cart cooking and selling breakfast items such as dosa and idli, when she met with an accident. Hot oil spilt on her leg, and refused to heal for a long time. She finally had to go to a private hospital in the city where the doctors had to remove one of her toes. The surgery cost her Rs 1.2 lakh, which she borrowed from an informal lender for 10% interest per month. She continues to have a persistent wound. “Everyday I put on the glove and do the dressing of this wound myself,” she said. She was first diagnosed with diabetes when she was pregnant with her second child more than a decade ago. She goes to the primary health centre (PHC) near her house every month, where her blood sugar levels are checked and she gets her medicines. The PHC staff with whom around 200 diabetics are registered informed us that the blood sugar levels among the diabetics rises above their usual levels during summer. “I follow everything the doctor says. I take the medicine and follow the diet. But my sugar levels are often not in control,” she said. Because of her uncontrolled diabetes and the persistent wound on her leg, Vidya had to give up working outside home. Vidit Panchal, a public health physician who has worked in several parts of rural India, and with poor and tribal populations, said more evidence needs to be generated related to effects of extreme heat among people living in informal settlements. “There is not much primary evidence from different parts of India on how heat is impacting health outcomes of people