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Current high temperatures can put significant stress on people with chronic illnesses, including those with diabetes, and may affect diagnostics and therapy. Several experts explain what people with diabetes and their clinicians should pay attention to during extreme heat.

High-Risk Groups

“The body’s own temperature regulation is often impaired in people with diabetes. The body normally reacts to heat with increased blood flow to the skin and sweating. But these very mechanisms are often disrupted in people with diabetes — especially if nerve damage (neuropathies) or impaired kidney function is already present,” explained Jacqueline M. Ratter-Rieck, PhD, research associate at the Institute for Clinical Diabetology at the German Diabetes Center (DDZ), Düsseldorf, Germany.

In addition, people with diabetes are often burdened by cardiovascular comorbidities. Other conditions such as hypertension, cardiovascular disease, or chronic kidney disease make it more difficult to adapt to high temperatures. The consequence: the risk for overheating, circulatory collapse, or even life-threatening heatstroke rises.

“Data show that hospital admissions increase by up to 25% during heat waves. Therefore, people with diabetes who are older, overweight, or have high A1c (long-term blood glucose) levels and are treated with insulin should be particularly careful,” said Thaddäus Tönnies, PhD, head of the Junior Research Group Diabetes and Environment at DDZ.

Heat Affects Diabetes Therapy

Heat affects not only circulation but also the effectiveness of medications. Diuretics, beta-blockers, and certain antidepressants, often taken by people with diabetes, can further reduce heat tolerance and increase the risk for dehydration or a heart attack.

“High temperatures and water loss reduce insulin effectiveness and thus worsen blood glucose levels in diabetes, so diabetes therapy should be tailored to the individual. Whether and how medications should be adjusted in extreme heat must be discussed with the treating physician,” explained Michael Roden, PhD, scientific director and board spokesperson of DDZ and director of the Clinic for Endocrinology and Diabetology at the University Hospital of Düsseldorf.

“In addition, heat can accelerate the absorption of insulin in the body — which can lead to dangerous hypoglycemia. At the same time, dehydration affects insulin signaling pathways and can lead to poorer blood glucose control,” Ratter-Rieck added.

A comprehensive overview of medications that may affect temperature regulation and fluid balance during heat waves is provided, for example, in the Heat Manual of the German Association of General Practitioners.

How People With Diabetes Can Protect Themselves

To stay safe during extreme heat, diabetologists recommend the following measures:

Adjust daily routines and protect from sun exposure. Schedule activities for early morning or late evening. Swimming poses a high risk because adrenaline release can mask typical hypoglycemia symptoms such as trembling, palpitations, or restlessness. Water may also feel pleasantly cool, masking sweat loss.

Stay hydrated. Drink regularly even without thirst (not universally recommended for patients with chronic kidney disease). Nutritionist Theresia Schoppe from the German Association of Diabetes Counseling and Training Professionals noted that heat adds another risk factor for blood glucose self-monitoring beyond the direct effects of heat on devices and test strips. Dehydration alters blood hematocrit, which can affect readings.

Avoid walking barefoot. Peripheral neuropathy can increase the risk for injuries, including burns.

Check blood glucose more frequently. Heat alters metabolism. Physical activity may trigger both hyperglycemia and hypoglycemia.

Keep insulin at 36-46 °F (2-8 °C). Never store medications in direct sunlight. Special cooling pouches are available for insulin pens, which can be carried in hand luggage during flights with a medical certificate. Blood glucose meters and test strips should also be protected from heat and sun exposure, Schoppe advised.

Insulin Pump Use During Heat Waves

Insulin pumps should be used according to manufacturer-specified temperature ranges. All pump types are most vulnerable in the insulin reservoir. Patch pumps worn close to the body may experience less temperature difference, but tubing pumps can also be worn near the body to reduce heat exposure.

Schoppe emphasized that insulin in infusion sets is heat sensitive. Denatured insulin loses its structure, clogs tubing or cannulas, and can compromise delivery accuracy. Introducing cold insulin into a reservoir at high ambient temperatures may cause expansion or air bubbles, further affecting dosing. She recommended keeping pumps under clothing and close to the body during heat waves.

Pumps with automated insulin delivery functions are particularly sensitive, as heat may affect both real-time continuous glucose monitoring (rt-CGM) sensor accuracy and insulin delivery, as well as insulin activity. However, concrete studies are still lacking.

Control devices for rt-CGM systems or insulin pumps with integrated batteries or removable cells must also be protected from extreme temperatures. Recommended storage is typically outside 32-86 °F (0-30 °C) and operation within 41-104 °F (5-40 °C). Only manufacturer-supplied chargers should be used, and the user manual should be checked. High temperatures may cause batteries to ignite or explode, Schoppe warned.

This story was translated from Univadis Germany.