Michael Ring was organizing a 100-mile bike tour in Putnam County in 2014 when he started falling, dropping things and tripping over stuff — it was happening so often that his then-boss took notice.

“He took me aside and said, ‘I don’t talk about this, but I’m a cancer survivor. I’m saying that to scare you. Call your doctor. This is weird,'” Ring, now 61, recalled to The Post.

The Brooklyn native saw a doctor and the news wasn’t good — he was diagnosed with Guillain-Barré syndrome. His immune system was attacking his nerves, temporarily paralyzing him.

Ring spent 135 days in the hospital and had to relearn how to walk. Now, he is preparing to toe the line at Sunday’s TCS New York City Marathon, a 26.2-mile course he knows all too well since initially tackling it in 1980.

It takes him twice as long these days — he sports ankle braces and runs with two volunteers from Achilles International, a non-profit that supports athletes with disabilities.

“I’m going to start 40 minutes before the elite men, and everyone’s going to pass me, all 55,000 people,” Ring said. “My Achilles guides are like my offensive linebackers. They’ll run behind me for the first half of the race so that people don’t crash into me in the second half of the race.”

The Park Slope father of two was a senior at Sheepshead Bay High the first time he attempted the NYC marathon. A self-described “spaz,” he joined the track team to be able to skip gym class.

He ran the marathon without training or coaching — and it didn’t go well.

“I went out too fast and then drank a lot of water in Queens and threw up off the Queensboro Bridge,” Ring shared, admitting he dropped out at mile 16.

He gave up running but eventually got back into the sport in the early ’90s. He ran the NYC marathon from 1993 to 2013 — setting a course personal record of 4 hours and 11 minutes in 1994 — and was signed up for 2014 when disaster struck.

Ring took a road trip in April 2014 to spectate the Boston Marathon — that race was particularly special because it was the first after the 2013 bombing.

Afterward, he and pals grabbed dinner at a “hole-in-the-wall” barbecue joint. He had chicken. He doesn’t remember the name of the place, and he’s not exactly sure that’s where he got sick.

But he had a three-day bad bout of food poisoning that changed his life forever. Food poisoning from Campylobacter, a type of bacteria that can cause diarrhea, is one of the most common triggers for Guillain-Barré.

Some 3,000 to 6,000 Americans develop the disease each year, usually after experiencing a respiratory or gastrointestinal infection.

“If you take all people with Guillain-Barré, it’s usually said about 20% of people have a poor outcome, which we often define as being unable to walk unassisted at the six-month [mark],” Dr. Thomas H. Brannagan III, director of the Peripheral Neuropathy Center and co-director of the EMG laboratory at Columbia University Medical Center, told The Post.

Ring, unfortunately, has acute motor axonal neuropathy, a very rare variant of Guillain-Barré that typically means a faster onset of severe muscle weakness.

He underwent intravenous immunoglobulin, receiving antibodies from healthy donors, and off-label chemotherapy before facing a long road of physical therapy.

“Doctors would ask me to wiggle my toes, and I’d look at the doctor, I said, ‘Why don’t you ask me to wiggle your toes?’ I just couldn’t. I’d look down at my feet, and they didn’t move,” Ring said.

Eventually, he was “clunking around” — now he wears carbon-fiber ankle braces because he has trouble lifting the front part of his feet. They also keep him from turning his ankles.

He typically visits a physical therapist every two weeks, though he admits his healing has “leveled off.”

He’s had about 10 surgeries in the last decade — his fingers were shaped to make it easier to hold things like cups and pens and some bone was removed from his right foot so he didn’t bang the ball of it against the orthotic.

Ring trains by running carefully two or three days a week, as just one fall can derail his progress. He’s found a lot of success using the elliptical machine, where can take off his orthotics and work up a sweat because his feet don’t leave the plates.

The disability rights advocate, who sits on the NYC Advisory Committee for Transit Accessibility, got back into marathoning in 2017 and has completed several races since then. He finished last year’s NYC marathon in 8 hours, 36 minutes and 15 seconds, a pace of 19 minutes, 42 seconds per mile.

Sometimes he doesn’t always finish, and that’s OK. He quit the PPTC Endurance Fest 50-kilometer race last December around mile 13, out of 31, because he was soaked from the rain. He said to himself he would heal up and finish another race.

“When I was in the hospital, missing races, missing the things I registered for, a shrink came in to chat with me, asked me what was important,” Ring said.

“My twins were 14 at the time. I want to be a role model. And she’s like, ‘Well, we got to figure out a different way for you to be a role model,'” he continued. “Now, I just figure, I got to show them that you might fall into a big hole, and you got to try to climb out.”