Literally “asking for a friend” Since I ran out of ketomojo strips I dont even care about blood ketones since I can sort of tell from how I feel. But my friend still reads lots of articles and the “optimal ketone level for weight loss” varies from 0.5-3.0 to 1.5-3.0 to >1, etc.
Any actual facts? My guess is YMMV would be the rule.
TIA
Phinney and Volek define “nutritional ketosis” as serum β-hydroxybutyrate between 0.5 and about 3.5. Values in fasting ketosis tend to run a bit higher. This is probably the basis for what your friend has read.
Dr. Phinney and Prof. Volek have both admitted that the 0.5 is fairly arbitrary; they picked it simply because its a level at which they observe beneficial effects. Dr. Phinney once said in a lecture at Ketofest that it is possible that 1.0 is better than 0.5 for fat loss, but levels higher than that don’t seem to confer any additional advantage.
The experience of people on these forums bears that out. Many of us have remarked that the rate of our fat loss seems to bear no relationship to our ketone level.
I should have added that if insulin is high enough to prevent ketogenesis, then it is also high enough to prevent fatty-acid metabolism. So the first thing is to get insulin down by not eating too much carbohydrate. There are other issues, but this is the most important one.
No such thing, literally. I rarely ever went above 0.3-0.5 and lost 100lb in a year. If ketone levels mattered that way we could just drink exogenous ketones a couple times a day and melt it all off.
in my personal exp. ketones do not matter. if you keep carbs below a certain level. my ketones rarely register above 0.7 on the blood test. even if i fast or go pure carnivore.
you still need to watch calorie intake on keto. that point is missed by many. naturally people under eat on keto, but not all. i log everything into myfitnesspal to make i got the protein in.
I strongly believe that ketones matter significantly … but let me explain what I mean:
Perhaps putting too fine a point on it (or stating the obvious) but when we talk about ketone levels, we’re typically talking about the level that has NOT yet been utilized by tissue/muscle/brain - and is still circulating in the blood (or excreted in the urine) - depending on how we’re measuring.
Ketones do no good unless and until they’re taken up by the organs and muscles in connection with being converted into energy by mitochondria that are adapted (from having otherwise created energy largely from glucose).
So when we talk about our measured ketone levels, what we are measuring is what is available for measurement because it is UNUSED as of that moment.
Having a low ketone blood level while losing all that weight would strongly indicate that your body became highly efficient at utilizing ketones. There wasn’t much leftover to circulate in your blood serum (or to urinate away).
Ketones mattered greatly. In fact, your body made them from about 100 lbs of stored energy in your adipose tissue.
Having cut out the carbs, if not for ketones you’d be dead by now.
Win for the team! 
Do you feel like we need to measure ketones, if we are eating low or zero carb? I never saw the need.
It’s a fair question to consider. “Need” is often just a stronger form of “want.”
For data geeks (like me), we feel the need to gather statistics about things that interest us. And little interests most people more than themselves. 
After a while, even the most devout self-data gatherers lose interest and move on to other data gathering prospects. When we do, we realize that what we “needed” was really just what we “wanted” … and when we lose interest, we want some other data to need. 
I fully support those who need to measure their ketones. And I fully understand why they really don’t need to do so. It’s all good.
Just wondering. Wouldn’t higher ketone levels be more likely to reflect burning of stored fat rather than dietary fat? The way I see it, dietary fat is also metabolized to ketones, so people who are only maintaining (not losing) their weight on a high fat diet would have the lower level in blood (because how much fat can you eat at one time?), whereas people burning stored fat in addition to consuming dietary fat might reach higher levels.
Apparently not. Dr. Phinney says that his data show that a level of 2.0 is not correlated with any greater benefit than one of 1.0.
He also has data to show that, the more fat we eat, the greater our fatty-acid metabolism increases, so that we are metabolising more body fat, not less. Now, I’m sure there’s a limit with that, but someone eating to satiety and stopping eating is not likely to hit that limit. Prof. Bikman discusses this process, which is known as mitochondrial uncoupling in the adipose tissue, whereby fat cells burn far more energy than they need to survive on. Lowering insulin is what enables this.