“Why does my ketone level fluctuate?”


Why does your ketone level fluctuate? How do you know that your body has reached its ideal weight? How can you ensure that you get enough nutrients when fasting? And will your metabolism slow down if you eat too few calories?

Get the answers to these and other questions in this week’s Q&A with me.

Please note that these answers do not constitute medical advice and no doctor-patient relationship is established. These answers are for general information purposes and you should discuss any changes with your healthcare provider.

Fluctuating ketones & ideal weight


I’ve been in continual ketosis for about two months. I use a blood meter to check, usually twice a week. I practice intermittent fasting daily. In addition, I fast from dinner to dinner twice a week consuming only liquids throughout the day including water, coffee, and bone broth. Sometimes my ketones are higher after a fast day, sometimes as high as 2.2 mmol/L and other times as low as 0.6 mmol/L. Can you explain why?

Also, I can’t seem to lose the last 5 or 6 pounds (2-3 kg) I’m trying to lose. I know my body is supposed to find it’s own level. How do I know when I’ve reached my ideal weight? I’m 5′ 11″ (180 cm) and 180 lbs (82 kg). I’m turning 64 soon and the “experts” say I should have a bit of extra belly fat as I age. But I don’t want extra belly fat. LOL.


Great questions, Mark.

Ketone levels can fluctuate based on many things including fasting, exercise, sleep pattern, stress level, and more. That can make it hard to predict what your ketone levels will be from day to day. However, a bigger question is, does it matter?

When it comes to health and weight loss, there likely isn’t any benefit to higher ketone levels. That may be different for treating neurologic conditions like Alzheimer’s or brain trauma, but that research is still being done. For most of us, however, a 0.6 is just as good as a 2.0 as it shows we are burning fat for fuel.

As for your weight-loss progress, here are two guides that may help you set your expectations and put it into perspective. I hope they help!

Weight, health, and happiness

Setting realistic expectations

Dr. Bret Scher

Enough nutrients when fasting?

I started LCHF and fasting last week and lost 9 lbs (4 kg). I’m beyond delighted, but worried about nutrients.

I eat one to two meals a day, usually within a 4-hour window, but what I eat may not have all the fiber, iron, calcium, potassium, magnesium, etc. that my body needs.

I eat mainly green veggies, fat, and protein (and take protein whey as a supplement) and I eat severely under the recommended calories (I have been eating on average under 800 calories per day because I’m simply not hungry – the magic of ketosis).

I can take vitamin supplements, but would prefer to know how to balance the food I’m eating to get these naturally.


Congrats on your progress thus far. You bring up a great point about making sure you get enough nutrients. We addressed some of those concerns in our OMAD guide.

The first key is making sure you get enough protein. The second is making sure you get enough micronutrients. If you are eating a balanced diet with veggies and animal products, you are likely getting all that you need.

If there is still a concern, then a multivitamin may be a good option. As for things like fiber, we don’t know that there is any requirement for fiber on a low-carb diet. All of the studies have looked at higher-carb diets.

Dr. Bret Scher

Will eating too few calories slow one’s metabolism?

Hi there.

I’m successfully eating keto and doing the 16/8 fasting on most days. Sometimes it’s really hard for me to eat very much (today I got in about 400 kcal, 20 g protein, 31 g fat). I’m concerned that my metabolism could slow down. Suggestions?


Great question, Victoria. There is a definitely a point where time-restricted eating or intermittent fasting start to mimic chronic caloric restriction, which can slow resting metabolic rate. We tried to address that in our OMAD guide, but the truth is that there is no great way to predict it other than measuring it. I would suggest you find a place that performs these tests and check yours a few times per year.

Also, as we cover in our OMAD guide, not getting enough protein can be a concern with fasting. I suggest you look into that as well.

Last, you could consider working with a healthcare practitioner familiar with these concepts to give you more specific guidance, try our find a doctor map to see if you can locate one that works for you.

Dr. Bret Scher

More questions and answers

Many more questions and answers:

Low-carb Q&A


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