“I’m lucky that I want to do this and I can do this,” Ms. Bowler said. “A lot of other people, I don’t know what they would do. People in this case say, ‘Look, at the end of the day, whatever happens, I can spend a ton of money but he’s still going to die.’ I just always want to beat the odds if I can.”

Alana Yañez of Highland Park, Calif., faced a similar decision in October, when her 11-year-old yellow Labrador retriever, Max, started limping. Ms. Yañez, 34, works with the Humane Society of the United States’ Pets for Life program, which provides free training and veterinary care to low-income communities. She counsels clients almost daily about end-of-life care for their pets and did the same in college while working as a veterinary technician. But she still faced wrenching decisions when it came to her own animals.

Max was found to have a tumor that was pinching his colon and compressing his spine. Chemotherapy could keep the tumor from growing, at least for a while, but would cost a minimum of $10,000. “It would have been a really long and hard process,” she said. “And when we’re in this situation, excuse me, you get so caught up in the emotion that at one point I just stopped” and said to her veterinarian, “Tell me what to do.”

The vet told her that unless she had about $40,000 available for all the medicines and follow-up care Max would need, she should think about euthanasia. Ms. Yañez and her mother decided not to put Max through any more pain. They went to a craft store and got supplies to immortalize the dog’s pawprints in clay, then had a service come to her apartment to put Max to sleep.

Ms. Yañez is in a unique position to understand how lucky she was even to have a decision to make. The clients she works with in low-income neighborhoods often have no choice but to euthanize their sick pets; they cannot afford even basic treatments, much less the expensive lifesaving options other pet owners must choose from.

Ms. Yañez and her mother spent days deciding what to do about Max. Her clients do not take as much time. “The reality of not having money to take your own child to the doctor, not have enough money to buy groceries,” she said, “the conversation is not very long.”

But having resources doesn’t blunt the agony. “I still sometimes struggle with whether or not we made the right decision,” she said. “Putting $10,000 on a credit card — I could afford it. But what stopped me was thinking about my auntie who had breast cancer.” Recalling that as “horrible, the most brutal treatment,” she said she decided not to make Max go through chemotherapy. “And the chances of him living weren’t guaranteed, either,” she added.