Heather Menzel squirmed in her seat, unable to sleep on the Greyhound bus as it rolled through the early morning darkness toward Bakersfield, Calif. She’d been trapped in transit for three miserable days, stewing in a horrific sickness only a heroin addict can understand. Again and again, she stumbled down the aisle to the bathroom to vomit.

She hadn’t used since Chicago. She told herself that if she could just get through this self-prescribed detox, if she could get to her mother’s house in her hometown of Lake Isabella, Calif., all her problems would be solved.

“I’ve been through a lot of horrible, crazy stuff,” said Menzel, now 34. “I’ve been raped. I’ve been beaten up. I’ve been in prison. But trying to kick heroin on the Greyhound on the way home was the worst experience of my entire life.”

When Menzel finally arrived at the Bakersfield bus station at 6 a.m. that day in February 2014, her mother and stepfather were there waiting. The two women hadn’t seen each other in years, not since Menzel stole her mom’s jewelry and fled the area. They didn’t talk much as they drove east toward Lake Isabella, a two-stoplight town with a population of 3,500 nestled in the golden Sierra Nevada foothills.

Menzel hoped that the worst of the withdrawal was over — that a new life without heroin awaited. What she didn’t know was that heroin was now cheap and plentiful in Lake Isabella, and that her best hope for ­treatment was far away.

Experts recommend medication-assisted treatment for drug users like Menzel, one of nearly 2 million Americans struggling with opioid addiction. MAT, as the therapy is known, has been proven far more effective — and less dangerous and miserable — than cold-turkey quitting. Drugs like methadone and buprenorphine can help suppress opioid cravings and stave off the symptoms of withdrawal.

When carefully managed, MAT can cut the risk of overdose death by half, research shows. But not all medical providers are properly trained and approved to provide the treatments, which themselves are opioids (albeit less likely to be abused).

Lake Isabella sits in the Kern River Valley, home to 32 churches but not a single methadone clinic or doctor able or willing to prescribe buprenorphine. Like half the counties in California, it is an opioid “treatment desert.”

“In rural areas, historically, there has been a lot of stigma around addiction treatment,” said Kelly Pfeifer, a primary care doctor and opioid project director at the California Health Care Foundation. “Although the state is trying to remedy this, there are still wide treatment deserts across California.”

Without such help, many experts say people like Menzel barely stand a chance.

From the beginning, Menzel struggled to stay clean at her mother’s. She soon fell back in with her drug-abusing friends. Within two months of arriving home, she was hooked on heroin again, smoking methamphetamine and, once her mom kicked her out, homeless.

She was risking death, and she knew it. On average, 91 people a day in the United States died of an opioid overdose in 2015, the latest figures available from the Centers for Disease Control and Prevention, and projections show the death rate will continue to rise.

Immediate, convenient access to these treatments is key. “It is very important for someone in the middle of addiction to access treatment when they are ready,” said Pfeifer. “There are these moments when people have wake-up calls — when they are ready to seek care and get out of the chaos of trying to get drugs to feel normal again.”

Menzel’s wake-up happened when she noticed that she was still sick after a morning heroin injection. After an angry call to her drug dealer to accuse him of ripping her off, Menzel soon realized it wasn’t fake heroin — she was pregnant.

She took the bus to the emergency room in Bakersfield, where a doctor told her, “If you want to save your baby, you need to get on methadone.”

Affording methadone wasn’t a problem for Menzel. Medi-Cal, the state’s version of the Medicaid program for the poor, covered the costs. What impeded her was the daily trip from Lake Isabella to Bakersfield — an hour-plus bus ride. A round-trip ticket cost $5, more than she could spare.

“The fact you have to travel an hour to two hours every day to receive treatment requires somebody to operate a vehicle, pay for gas, and for some of our patients that is impossible,” said Javier Moreno, who manages the narcotics treatment programs in the Central Valley for Aegis Treatment Centers.

Eventually, Menzel’s cravings for heroin subsided. After a couple of months, she was able to get “take-home” methadone doses for the weekend. She started riding the bus again to give her mother a break.

“I was big and pregnant,” said Menzel. “I had to ask the bus driver to pull over and pee a lot. But I made it.”

In May 2015, Menzel gave birth to a healthy girl, Bella. She said she hasn’t used heroin or any other drug, besides methadone, in more than two years. She’s on a maintenance methadone dose, just 39 milligrams compared with 140 mg she used to take, and plans to cut back until she is off it completely. She drives herself to the clinic every other week and has enrolled in community college, hoping to become a drug and alcohol counselor.

“I really want to work with other pregnant women who will be going through the same thing that I went through.”