Want to feel smug? Roll of out bed in Byron Bay and check the Melbourne weather. During the week, the screen showing Melbourne had a black background and white dots, which indicates very cold rain and dark skies.

Lol, I thought, as I opened the curtains and was suddenly bathed in the sort of sun used in religious paintings around the depiction of Jesus or the saints.

Byron Bay in winter! It’s a holy place. Having just written a book on wellness I knew that Byron Bay was where wellness people came to die. Or else retire at 27. They make all their money in their early 20s Instagramming swimwear and move up here and work for three hours a week consulting on farm-to-table restaurant menus and have gorgeous, blonde children called Popsy.

It’s also where sick people come to get well. Later in the day I would be visiting a residential drug and alcohol detox centre for a story, and spending the night at the facility to get a closer handle on what happens to people who want to go clean.

But first I went down to the beach – walked for hour or so, went for a swim and then checked the Melbourne weather again and it was still sleeting and black so I Instagrammed a photo of the beach set to the brightest filter, went for another walk and swam in a tea tree lake that ran into the ocean (although the lake was shallow so I sort of scraped along the bottom). And I swore I was getting a bit sunburnt and tweeted “Sunburn! Lol! Byron!”

I was feeling so virtuous (12,000 steps and two swims before breakfast) that I stopped at a cafe and ordered the healthiest thing on the menu – a vile-looking green juice. It was 11am and the cafe was full of tanned, relaxed people with their dogs drinking turmeric lattes (the people, not the dogs – mostly). Did no one work in this town? I had found my tribe.

This juice was made of spinach, kale, cucumber, zucchini and a few other vegetables. I drank it in one gulp. Almost immediately I began to feel incredibly ill. It was like someone had inserted a vice into my intestines and was squeezing very hard.

Sweat was pouring off me, not in a nice, yoga way but in an ill, violent way. I should have ordered a can of Coke.

I fled the cafe and threw up on the side of the road. But it was only the start of my woes.

Feeling close to collapsing, I went back to my room. I had to lie down for a bit. I rang the rehab place. “I’ll be late. I’m feeling very sick and feeble.”

They were understanding and spoke to me in the professionally soothing tones. I packed in a fever: one tennis shoe, a novel I had already read, mismatched socks.

Once in the car the bumps on the road were making things worse; “Euggh, orf,” I said. “I don’t feel so great”.

Once at the centre, I had to keep ducking to the loos to be sick. I couldn’t keep any food down. In the tai chi session the teacher took it slowly as I complained about the pain, and she said: “Feel into your belly. Just breathe.”

I took to my bed at 7.30pm but keep waking up confused, disorientated, ill and sweating. Where am I? I asked myself in panic. Who am I? What am I doing here? Why didn’t I pack my pyjamas? What had they put in the juice? Polonium? I took a 2am shower. I had a cold bath with Epsom salts. I took comfort in the fact that this was, after all, a detox facility and the sheets were changed daily.

I woke again the next morning, in a strange room, to the brilliant, clarifying Byron sun. I didn’t feel like going to the beach. I never wanted to see another green juice in my life.

“Another day in paradise,” I muttered bitterly to myself. I was still feeling sick.

I didn’t check the Melbourne weather but I suddenly longed for dark rooms and low lamplights.

That was yesterday. I’m OK now and back in the City of Sleet – and except for the interview notes made with a shaky hand, it could have all been a dream.

• Brigid Delaney’s Wellmania (Nero, $32.99) is out now