The percentage of overdoses involving heroin is on the rise in Arizona.

The Arizona Department of Health Services’ opioid dashboard shows last year heroin was found in nearly 29% of overdose cases across the state. It has spiked to 43% so far this year.

Christina Orellana, a primary therapist at Scottsdale Recovery Center, pointed to a possible reason.

“One thing that I’ve heard now a few times is this false belief that heroin is not going to cause an overdose as long as it’s not laced with fentanyl,” Orellana said.

“The flaws in that is, one, you don’t know if it’s going to be laced with fentanyl and, two, you can overdose and die from heroin without it being laced with fentanyl.”

The state health department’s opioid dashboard shows the percentage of overdose cases involving fentanyl have decreased slightly, while those involving cocaine or hydrocodone have seen bigger drops.

There has also been a rise in the number of overdose cases involving only one drug. Last year it was 52%, and so far this year it’s 62%.

Orellana said accidental overdose “happens all the time.”

“I’ve worked with many patients who have overdosed and have, thankfully, been revived and come into treatment,” Orellana said. “Their intention was not to overdose. They thought that they could control what they were using.”

Orellana also warned it’s hard to know what exactly is in the drugs people are using. Some drugs may be mixed with other substances, which can cause fatal overdoses.

She added people’s bodies change as their addiction progresses, so “the way that a drug is impacting you is different every day as your disease progresses.”

“It’s not a science, and thinking that you can control it and know what is going to happen is false,” she said.

Orellana encouraged anyone with an addiction to seek help.