Unless you replenish fluids, just an hour's hike in the heat or a 30-minute run might be enough to get mildly dehydrated, scientists say. RunPhoto/Getty Images hide caption

Wren Vetens was promised a significant discount on the cost of her gender-confirmation surgery if she paid in cash upfront, without using her health insurance. Yet afterward, Vetens received an explanation of benefits saying the hospital had billed her insurer nearly $92,000. Lauren Justice for KHN hide caption

A blacklegged tick like this one can be hard to spot. Scott Camazine/Science Source hide caption

Describing how pain affects your daily activities may be more effective than the standard pain scale. Lynn Scurfield for NPR hide caption

When the heart pushes too hard, as it does when blood pressure is elevated, it can cause damage that can lead to a stroke, says Dr. Walter Koroshetz. John Rensten/Getty Images hide caption

Time outdoors leaves you vulnerable to tick bites and the diseases they can transmit. New research seeks to a better picture of the geographic spread of ticks that carry dangerous pathogens. Ascent/PKS Media Inc. via Getty Images hide caption

"Don't come near me until the permethrin on your clothes has dried." Manuel Breva Colmeiro/Getty Images hide caption

When ticks come into contact with clothing sprayed with permethrin, research shows, they quickly become incapacitated and are unable to bite. Pearl Mak/NPR hide caption

Alan Dambach developed tremors that caused his hands to shake uncontrollably. His condition made it difficult to work on his family's tree farm in Fombell, Pa. Ross Mantle for NPR hide caption

Arnaldo holds a toy truck, his stim toy. Norma Molina for WNYC hide caption

Vaginal smear test at the gynecologist's office. BSIP/UIG via Getty Images hide caption

Sunscreens containing minerals like zinc oxide and titanium dioxide reflect the sun's rays away from skin and are a good alternative to chemicals that could be harmful to ocean reefs. Photo illustration by Eslah Attar/NPR hide caption

Angel Dean Lopez and his son Theo both sustained serious injuries to their hands that required surgery and months of occupational therapy. Heidi de Marco/Kaiser Health News hide caption

A vaccine given during pregnancy protects the baby against whooping cough, but only about 50 percent of pregnant women get it. Nicole Xu for NPR hide caption

Communities and online social networks can be beneficial for kids, a researcher says. Michael Zwahlen/Getty Images/EyeEm hide caption

Stephanie and Natalie enrolled their older son in sessions at a Brain Balance Achievement Center in the hope that it would help him make friends. Hokyoung Kim for NPR hide caption

Rita Steyn has a family history of cancer so she ordered a home genetic testing kit to see if she carried certain genetic mutations that increase the risk for the disease. Courtesy of Rita Steyn hide caption