As a heat wave sweeps over much of the country, with triple-digits possible in some places, the high temperatures carry an extra risk for millions of people taking GLP-1 medications like Ozempic or Wegovy.

The big worry doctors are warning their patients about? Dehydration that could lead to heat illness, heat exhaustion or worse. 

(MORE: Record heat for Plains, East, Northwest)

Why GLP-1 users are more vulnerable

• Reduced water intake

The most obvious reason GLP-1 users are more prone to dehydration is that while the drugs suppress hunger, they also suppress thirst. “So they’re just taking in less water than everybody else," explains Dr. Zaid Fadul, founder and CEO of Bespoke Concierge MD.

• Increased fluid loss

Then there are the side-effects that many users experience: nausea, vomiting and diarrhea, “You’re losing fluid much, much more than you realize from that mechanism. So you’re taking in less, you're putting out more,” Dr. Fadul says.

• The hormonal wildcard

For a small fraction of GLP-1 users the medications may also lower the production of vasopressin, says Dr. Fadul, a hormone that helps your body retain water.  The research on this is still emerging and not fully understood, he explained, “So you've got all these different things that are kind of piling up  to set you back.”

(MORE: Warning Signs Of Heat Illness)

‘Don’t trust your senses’

Dr. Fadul says he has some simple rules that he gives to all of his GLP-1 patients, his first is:

• Don’t trust your senses 

“Don't assume that your body is telling you when you’re thirsty. When you're on a GLP-1, you may not realize that you're thirsty because everything is being suppressed.  So that's why I try and get patients to just automatically drink.”

(MORE: 5 Things To Stay During A Heat Wave)

• Trust your countermeasures

Dr. Fadul suggests setting an alarm on your watch or your phone to remind you to drink a glass of water every 90 minutes, “Or at the max every 120 (minutes), just pick a number and stick to it.”

• Plan, Plan, Plan

“I want you to plan small meals frequently so that you don’t get dehydrated or hypoglycemic.” 

Choose foods that are hydrating and won’t cause your body to work harder to digest them – “Watermelon is one of our best things, and then cucumbers, super high and dense in water.”

This week’s heat wave is only the beginning of the hot temperatures most of us will have to endure this summer, so Dr. Fadul says these steps are great for all of us to prevent and avoid heat illness.