A 7-Day Journey Out of Ketosis and Back In

For about two months, I've been on a strict keto journey. I've been eating clean, tracking my food, and doing fasted exercise 6-7 days a week. The results have been great. But then, I caught a cold.

Even though I was sticking to the keto guidelines, my body was acting strange. My ketone values were lower, and my blood sugar was higher than it had been since I started. After three days of this, my morning ketone value was down to a meager 0.5 mmol/L. I felt like I was on the edge of falling out anyway, so I decided to do an experiment: instead of fighting it, I would lean into it. I would eat myself completely out of ketosis and document the journey back.

The goal wasn't to have a cheat meal; it was to learn about my own body's limits. If keto is going to be a lifelong commitment, it's good to know how flexible I can be. It doesn't have to be all or nothing. It can be almost all, with a tiny little bit of something else. This was my chance to find out what that looks like.

The Fall: Day 0

As my ketone value was already so low, I figured the fall wouldn't be too dramatic. For dinner, I ate what the rest of the family was having: hotdogs and French fries. To top it off, I finally consumed a small bag of candy I had been eyeballing.

The effect was almost immediate. A light dizziness came on, and I felt a bit more tired than before. It was pretty clear to me that while my ketosis was probably hanging on by a thread before, it was completely gone now.

My experiment officially began. I marked it in my keto tracking app, wishing in that moment that the app had a feature to flag important days (it now has this feature). It would make looking back through the logs so much easier.

The Plan to Return

My plan to get back into ketosis was simple and based on what I knew worked for me:

Longer night fasts combined with morning exercise to deplete glycogen stores.
Strict keto eating with under 20g of carbs for the rest of the day.
Morning-only blood tests for clean, fasted readings.

I set a goal for myself: the experiment would be complete when I felt the return of mental clarity and had a fasted morning ketone value of around 2.0 mmol/L.

The Log: A Day-by-Day Account

Day 1 & 2: The "Glucose Breath" Phase

Five hours after the carb-heavy meal, the dizziness and tiredness had worn off. I just felt... normal. Like I probably did before I ever started keto. The transition out seemed pretty painless.

The morning of Day 2, however, was different. They say "keto breath" is a thing, but I woke up with what I can only describe as "glucose breath." It's a taste in your mouth that is just ungodly, like the sugar you ate the day before has been rotting inside you overnight.

Morning Test (Day 2):

Blood Glucose 97 mg/dL, Ketones 0.2 mmol/L.

Notes: I felt my "normal pains" from a hernia getting worse. I suspect inflammation was playing a role, much like my cold symptoms felt intensified when my blood sugar first rose. A planned run was scuttled by a rough night with one of my kids, so I only managed a walk. I was feeling low on energy, but I had to remind myself I was getting back into keto while sick and sleep-deprived.

Evening Test (Day 2): I couldn't hold myself and did an evening test. Still 0.2.

Day 3 & 4: The Plateau and a New Theory

Morning Test (Day 3):

Blood Glucose 99 mg/dL, Ketones 0.2 mmol/L. No progress.

Notes: I managed a 50-minute run, hoping to deplete my glucose stores. I felt it was crucial to get back into ketosis quickly. There's a saying in the keto community to "marry, don't date" the diet, which I take to mean that the state of eating high-fat while your body is still running on glucose is an unhealthy place to be. You want to be in one state or the other, not lingering in the middle.

Morning Test (Day 4):

Blood Glucose 97 mg/dL, Ketones 0.2 mmol/L. Still stuck. A real disappointment.

Notes: This is where I had a breakthrough in my thinking. I realized the running was a mistake. My normal workout is a full-body circuit, and by only running, I was leaving all the glycogen in my upper body untouched. I needed to deplete glucose everywhere to force my body to switch over. This was a crucial note-to-self: running is fine once you're in ketosis, but not the best tool to get back in. I went back to the gym for my normal, full-body workout.

Day 5: The Turning Point

Morning Test (Day 5):

Blood Glucose 89 mg/dL, Ketones 0.3 mmol/L. Finally, progress!

Notes: For the first time, I felt like I was getting there. My body didn't look as "carb bloated." I stuck with my full-body workout routine.

Evening Test (Day 5): Another impatient evening test. 0.5 mmol/L! I was officially in light ketosis. I felt unexpectedly happy over this. Even though I had taken some MCT oil a few hours prior, I took it as a win. The engine had started.

Day 6 & 7: The Rollercoaster and a Huge Discovery

Morning Test (Day 6):

Ketones 0.4 mmol/L. A bit of a letdown after the previous night's high.

Notes: I went hard at the gym and fasted until 16:20. I kept my carbs for the day at only 5g.

Afternoon Test (Day 6): Just before breaking my fast, I tested. 0.8 mmol/L! A new high. This felt like a perfect "get back into ketosis" day.

The Discovery:

I realized two things had been messing me up besides the cold:

Some "zero" sodas have more carbs than others. I noticed too late that the Fanta Lemon Zero I'd had was a culprit.
I suspect the macros for the macadamia nuts in my tracking app are wrong(its important to enter the correct macros). I was eating more carbs than I thought.

Morning Test (Day 7):

Blood Glucose 90 mg/dL, Ketones 1.0 mmol/L.

Notes: Even though I hadn't hit my 2.0 goal, the mind clarity was back. It felt awesome. Again, I was reminded that the taste of carbs is not worth sacrificing this feeling.

Afternoon Test (Day 7): 1.3 mmol/L. I was solidly in ketosis.

Day 8: The Goal is Reached

Morning Test (Day 8):

Ketones 1.0 mmol/L.

Post-Workout Test (Day 8): A surprising dip to 0.3 mmol/L.

Afternoon Test (Day 8): Climbed back to 1.3 mmol/L.

Evening Test (Day 8): 2.5 mmol/L! I finally hit my goal.

Conclusion and Key Takeaways

This experiment was a success, not because I hit a number, but because of what I learned. It took 8 days to get from a carb-loaded meal back to my target level of ketosis, but the lessons were worth it.

Key Takeaways:

1. Full-Body Workouts are Key

For me, just doing cardio isn't enough to get back into ketosis quickly. Depleting glycogen stores from all major muscle groups with a full-body workout was the strategy that finally started moving the needle.

2. Beware of Hidden Carbs

This was a huge one. Trusting "zero" drinks can be a mistake, doublecheck the labels. Some times they are sneaky showing per 250ml instead of 330ml as an example. Also, make sure that you add the correct macros for your food in your tracking app.

3. MCT Oil Might Be a Crutch

This was my final, and perhaps most important, insight. Looking back, I think taking MCT oil might have delayed my progress. It gives your body an "easy" source of ketones, which might prevent it from firing up its own ketone-producing machinery. On the final day, I believe the combination of a hard workout (which used up all available ketones) followed by a long fast (which gave my body no other option) is what finally forced the big breakthrough.

In the end, this experience solidified my commitment. It showed me how my body reacts, what my personal levers are, and how to troubleshoot when things go wrong. And most importantly, it was a powerful reminder of the conclusion I reached on day one: nothing tastes as good as ketosis feels.