You’ve been on medication for years. The results keep coming back wrong. And every time you quietly wonder whether fasting is something your body could handle, something stops you. Maybe it’s the guidance. Maybe it’s the look on your GP’s face when you bring up anything outside the usual script. Maybe it’s just the assumption you’ve absorbed without realising it: that this kind of thing is for healthy people. Not for someone like you.
I had that assumption too. For years, it kept me away from extended fasting entirely.
Then January 2025. Eleven days without food. Blood tests before I started, blood tests during, blood tests after. On multiple medications when I began. And the results were not what the conventional framing had led me to expect.
I’m not telling you to do what I did. But if you’ve been on long-term medication and you’re wondering whether the data might look different from what you’ve been told, I think it’s worth seeing what mine showed.
The Assumption Nobody Says Out Loud
The conventional position on extended fasting and medication is, to be fair, a reasonable one.
If you’re on statins, blood pressure tablets, diabetes drugs, or anything that directly affects how your body handles glucose, the guidance is: don’t change anything dramatically without medical supervision. Some medications interact with fasting. Blood glucose can drop in ways that aren’t predictable. The body under stress behaves differently. I accepted that framing. For years.
But there’s an assumption baked into it that nobody quite says out loud. The assumption is that if you’re metabolically compromised, if your numbers have been heading the wrong direction, if you’ve been on long-term medication, extended fasting is a risk. Something for people who are already well. Not for people in the middle of the problem.
Prof. James Betts, metabolic physiologist at Bath and one of the sharper fasting researchers in the country, put it in a way that changed how I thought about this. His point was that throughout human evolution, dealing with intermittent periods without food was a basic survival requirement. The capacity to fast isn’t a specialist skill. It’s ancient. The medical caution is newer.
That doesn’t mean the caution is wrong. But it might mean, in some cases, it’s assuming fragility that isn’t there.
That’s what I wanted to find out.
Where I Was Before I Started
Let me give you the honest picture of where I was going into this.
December 2023. On six medications. Statins, ezetimibe, allopurinol, two asthma inhalers, antihistamines. Cholesterol at 8.0 mmol/L. That was after eleven years on statins. It was the highest reading I’d ever had. HbA1c at 46 mmol/mol, one point from the clinical threshold for a diabetes diagnosis. ALT, the liver enzyme that marks liver stress, was at 69. The upper limit is 40. I was at 173% of it. On statins. Supposedly being managed.
Not one thing heading the wrong way. Multiple things. Simultaneously. For years.
And in all of that time, on all of that medication, with results getting worse annually, not once did anyone suggest fasting. The advice was always the same: take the tablets, watch what you eat, come back in three months.
February 2024. I rang my GP. Told him I wanted to stop all five medications. Monitored. Blood tests every month. If anything spiked, I’d restart. He paused. Looked at my file. “Alright. We’ll track it closely.”
Twenty-one months later, I haven’t restarted a single one.
One month off statins, March 2024. The thing every article told me would happen, the cholesterol spike, the dangerous rebound, didn’t happen. Total cholesterol dropped from 8.0 to 7.0. Still high. But moving in the right direction without medication for the first time in over a decade.
I stopped my statins and waited for the spike. It never came.
What Eleven Months of Data Looked Like Going In
By January 2025, I was eleven months completely medication-free. HbA1c had come down from 46 to 40, out of pre-diabetic range entirely. I’d been doing 18:6 fasting as a daily baseline, multiple shorter extended fasts, and tracking glucose and ketones on and off.
The January 2025 fast was a deliberate reset. A kickstart for the year. January 9th. I stopped eating.
No formal GP conversation about this specific fast beforehand. I was tracking daily, I knew my biomarkers, and the body had adapted significantly over eleven months. That’s an N=1 judgement call, and I want to be clear about that. I’m not recommending anyone skip the GP conversation. For me, the data history gave me confidence.
What I tracked across those eleven days: weight daily, glucose and ketones where I could, how I felt morning and evening.
Day 2 was the familiar transition. Energy dipped. Slightly cold. Mild brain fog. Not surprising. Think of the early days of an extended fast like running a marathon in work shoes. You know the engine’s capable of the distance, but you haven’t changed into the right gear yet. Your body has spent years running on glucose, topping up every few hours. Asking it to switch fuel sources takes a day or two of grinding before it catches properly.
Day 4 was noticeably easier than previous fasts at the same point. Day 8, GKI, the glucose-ketone index, was at 2.7 at the 26-hour mark of one stretch, confirming therapeutic ketosis. By Day 11, the deepest ketosis I’d recorded: GKI 0.5, ketones 6.0 mmol/L, glucose 54 mg/dL.
January 20th. Eleven days in. Weight: 13st 12lbs. I’d gone in at 15st 2lbs. That’s 1st 4lbs over ten days and fourteen hours. All documented, all weighed daily.
Six Medications, Eleven Months, and What the Numbers Actually Said
“Six medications. Statins, gout pills, asthma inhalers, allergy tablets — the lot. I stopped all of them in 2024. Not because a YouTuber told me to — because thirteen months of blood tests told me the inputs were working. If documenting that kind of thing properly sounds worth following, subscribe.”
January 2025 blood tests, taken around the time of the fast. HbA1c: 40 mmol/mol. Normal range.
Let me put that next to what it was. October 2022, on six medications: HbA1c 47. December 2023, still medicated: HbA1c 46. January 2025, no medication, eleven months in: HbA1c 40. The direction doesn’t need much interpretation.
Creatinine, kidney function, had improved 13% in the first month off medication, back to optimal after eleven years of elevation. Liver enzyme ALT, 69 on statins, had dropped to 10 by November 2025. The upper limit is 40. I was running at 173% of it under medication. By late 2025, at 25%.
But here’s the part I want to include because honest data includes what went wrong.
Ferritin. Iron stores. December 2023: 141. January 2025: 18.40. April 2025: 8.90. A 94% drop. Very low. Iron deficient.
The obvious conclusion, that fasting caused it, turned out to be wrong. The GP flagged it, we investigated, and the cause was bleeding piles. Chronic blood loss from a haemorrhoid that had gone unaddressed. Nothing to do with fasting at all. It has since been removed. Ferritin is back to normal.
But here’s what I took from that: the blood test caught something that had nothing to do with the intervention I was doing. Regular monitoring caught a problem happening in the background that I didn’t know about. That’s exactly why you take the results to your GP, not just to check the things you’re changing deliberately, but to catch the things you didn’t know were there.
What This Data Actually Suggests
What my data suggests, and I want to be precise here, it’s one person’s data against NHS records going back to 2012, not a clinical trial, is that the body’s capacity to handle extended fasting doesn’t disappear because you’ve been on long-term medication. In my case, coming off medication and implementing extended fasting didn’t produce the metabolic crisis the conventional framing implied. It produced improvement across nearly every marker I track.
The conventional caution isn’t wrong. It’s incomplete. There’s a difference between “be careful, get supervised, monitor closely” and “this isn’t for people like you.”
That said, I want to be direct about one thing. If you’re on medication that directly affects blood glucose, specifically insulin, metformin, or sulphonylureas, extended fasting requires a proper GP conversation first. Blood glucose can drop dangerously. That’s a real risk, not a theoretical one. I told my GP afterwards precisely because some of those interactions are serious. This is not a post about stopping your medication. It’s about what the data looked like in my case, under supervision, with monitoring.
If you’re watching this without a diagnosis, bloods slightly off, energy not what it was, GP says “keep an eye on it,” here’s something worth knowing. The processes that were running in me for years before anyone put a clinical label on them don’t wait for the diagnosis to start. Insulin sensitivity, glucose regulation, inflammatory load: these are working right now, in everyone, years before a threshold gets crossed. Understanding how extended fasting affects those processes is useful before the medication conversation, not just after.
The mechanism that was running in me is, in all likelihood, running in you too.
I’ll leave that with you.
🎯 Key Takeaways
- The assumption isn’t always right: The idea that extended fasting is unsafe for people on long-term medication is a starting point for a conversation, not a conclusion. Supervised, monitored fasting produced improvement across most of my markers.
- The data before matters: Eleven months of daily 18:6, multiple shorter fasts, and regular blood testing gave my body and my GP the context to approach the January fast with confidence. This was not a standing start.
- Regular monitoring catches more than you expect: A blood test flagged a ferritin problem that had nothing to do with fasting. It was caught because we were watching. That’s the point of taking the numbers to your GP.
- GKI is worth knowing: By Day 8, my glucose-ketone index confirmed therapeutic ketosis. By Day 11, GKI 0.5. The metabolic machinery worked. The body adapted.
- The risk framing applies most specifically to blood glucose medications: If you’re on insulin, metformin, or sulphonylureas, the GP conversation isn’t optional. Blood glucose can drop dangerously. That’s a different situation to statins or antihistamines.
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⚠️ Important: This is educational content based on evidence and personal experience. It is not medical advice. Speak to your GP before making changes to your fasting pattern, diet, or medication.
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