I have been Ketoing again for 25 days. My period was a week late so I upped my calories, but kept my carbs below 25nc a day. Yet when I tested today (blood) my level was only 0.5mmoL/l. Its not because I upped my carbs, so what is going on!?
***Edited to add, I started the day after adjusting my caloric intake so I am wondering if the menstruation process affects the levels?
Ketone levels fluctuate throughout the day. I wouldn’t worry about it. If you are keeping your carb intake that low and are still breathing in and out, you are in ketosis. And besides, your serum β-hydroxybutyrate level represents the gap between what your liver is making and what your body hasn’t used yet. It doesn’t tell how much you are producing or using. As you reach the point of full fat-adaptation again, you will might also see your levels drop a bit, as your liver gets better at matching production to demand. But everyone is different, so who knows?
In other words, Keep Calm and Keto On. 
Many people’s cycles get a bit wonky at first because eating keto regulates hormones. But the first few months can be off as your hormones settle down. Most people find things are smoother than pre-keto once the adjustment period is over.
Sorry I don’t know anything about checking blood levels so I can’t answer your question, but I don’t think a late period at this stage is anything to worry about (unless there is some other reason for concern.)
That’s an interesting theory. I don’t think I’ve seen any real data on that.
I will say, however, that I gave up tracking ketones after years of doing so. I found the meters themselves not to be great (have one picture - somewhere - where I have three meters, one showing 0.2, one 0.4, and one 0.8). And, these values change for reasons that are not obvious.
Here is what I THINK should happen, though. If you are transitioning from lower calorie to higher calorie, you should get a higher ketone level initially (not sure exactly how long), because there is a “backup” of energy, and your body converts excess calories into more ketones. Dave Feldman experienced this:
Hypo = low calorie, hyper = high calorie, if you don’t know this.
To me, this explains a lot, including why if I ate a lot of fat one day, my ketones would (most times - again there’s a high variance) go up. I think it’s a “clogging” of the energy system.
