MANILA — Rayzabell Bongol, an 18-year-old mother and methamphetamine user, was afraid to die in President Rodrigo Duterte’s war on drugs in the Philippines. So she turned herself in to the police. They made her sign a pledge that she would never take illegal drugs again, then sent her home.

Once a week now, she is expected to attend a police-sponsored Zumba dance workout, where she gets a health check and a meal. Mr. Duterte “promised change,” she said at a recent class as three dozen other recovering addicts bopped and swayed to a blaring Latin beat. “As you can see, I am changing.”

Across the Philippines, the killing of some 1,300 drug suspects in the last two months has frightened hundreds of thousands of people like Ms. Bongol into turning themselves in. Officials cite the estimated 687,000 people who have surrendered, which vastly exceeded expectations, as evidence that Mr. Duterte’s deadly campaign is succeeding.

But the government is proving woefully unprepared to help the flood of users pledging to kick their habits, leaving almost all of them to battle addiction largely on their own. The country’s meager drug treatment facilities have been overwhelmed, creating a new crisis for Mr. Duterte as he presses ahead with his violent campaign to rid the nation of drug dealers.