As extreme heat continues across South Korea, with Seoul’s daytime high forecast to hit 39°C on August 7—Ipchu, the traditional seasonal marker signaling the start of autumn—heat-related illnesses are setting new daily records. Official statistics from the Korea Disease Control and Prevention Agency (KDCA) released on August 6 show that 49 heat-related illness cases occurred in Seoul the previous day, marking the highest single-day total recorded in the capital this year.
People with chronic conditions such as high blood pressure and diabetes need to be especially cautious, as extreme heat causes blood pressure and blood sugar levels to fluctuate more unpredictably than usual.
Dehydration and Medication Risks
During a heatwave, dehydration poses the single greatest danger to people with high blood pressure. When body fluids drop, blood pressure can plunge, reducing blood flow to the brain and triggering dizziness or diminished alertness.
To prevent dehydration when sweating heavily, experts emphasize drinking plain water frequently and in sufficient quantities rather than focusing on salt intake. Frequently consuming high-sodium brothy foods—such as naengmyeon (chilled noodle) broth—can instead cause blood pressure to spike.
Crucially, individuals on blood pressure medication should not stop taking their prescriptions on their own, even if they experience dizziness upon standing, severe palpitations, fainting, or lower-than-normal blood pressure readings.
"Even if your blood pressure measures lower than usual during the summer, you should never reduce or discontinue medication on your own," advised Lee Hae-young, a professor of cardiology at Seoul National University Hospital. "First, try replenishing fluids sufficiently. If your blood pressure still continues to measure low, the safest approach is to consult your medical team to discuss adjusting the dosage."
Patients taking specific classes of medication must pay even closer attention to fluid intake. Diuretics, which lower blood pressure by increasing urine output, carry an elevated risk of dehydration and electrolyte imbalances in summer heat. Similarly, SGLT2 inhibitors—oral type 2 diabetes treatments that lower blood sugar by blocking glucose reabsorption in the kidneys and excreting it in urine—cause additional fluid loss during glucose elimination.
Dietary Precautions and Heatstroke Warning Signs
Along with fluid intake, maintaining regular meal schedules is essential, as skipping meals impairs the body’s ability to regulate fluid balance. However, patients taking certain blood pressure medications should exercise caution with potassium-rich fruits and vegetables—such as bananas, Korean melons, kiwis, and tomatoes—because excessive consumption can raise blood potassium levels.
The drastic temperature gap between the outdoors and air-conditioned indoors presents another hazard during extreme heat. Sudden temperature shifts strain the peripheral blood vessels and the autonomic nervous system, placing stress on the cardiovascular system. On days when temperatures reach 35°C or higher, running the air conditioner to maintain a comfortable indoor environment is far safer than attempting to endure the heat.
"If your body temperature rises above 40°C and you exhibit abnormal behavior or changes in consciousness, you should suspect heatstroke and seek emergency medical care immediately," stressed Kim Tae-kyun, a professor of emergency medicine at Seoul National University Hospital. "During extreme heat, preventing dehydration with adequate fluid intake and rest is vital—never brush off warning signs from your body."
