Why ketones drop after workout?

(cheryl) #1

HI – doing a little experimentation today.

Took my ketones around 4:30 – and was at 1.3mml

I then went and worked out… took the level after…and was a 0.3mml…

I thought it would go up not down?

Any ideas?


(Duncan Kerridge) #2

Because you used them for energy in your workout. They’re only in the blood when they’re not being used.

Check the levels an hour later and they will likely be back to where they were before.

(cheryl) #3

lol… that makes total sense… DUH…

(Keri) #4

What type of workout was it?

I’ve found that if I do long-duration submax exercise (like swimming for an hour at a HR of 125-130) my glucose goes down and ketones go way up. If I do anything glycolytic (sprints or heavy lifting) my glucose goes up and ketones go down.

(What The Fast?!) #5

Same - shorter intense workouts = lower ketones afterwards. Longer endurance = higher ketones afterwards.

(cheryl) #6

I do circuit training – Today’s training was 15 min of lifting (a mix of upper and lower) then 15 min of cardio (HIIT) – then another 15 of lifting and followed by more cardio.


Well I have the same problem after strength training from 1.1mmoler to .3 and if I just searched for this topic it would of saved me $1 for the test strip I used.

(Ny Steel) #8

Hi knew here and glad to be here have lots to learn I know. Been doing intermittent fasting now since the lockdown started back in March. 16 hour fasting I do. I ate good nothing crazy… I started at 210 that got me to about 180 hit a plateau… So now I still fast but have now for past 3 weeks start keto… Been taking blood readings for about week now rather than strips I was at first.

Today was the first reading after I did arms and abs for first time or basically any anaerobic activity and the reading was .4

I get really critical on myself cause I was thinking the few strawberries I added to my salad did that lol… So it is ok to get a low reading after working out.

(Bob M) #9

I have found that, in general, my blood sugar goes up and ketones go down (or stay stable) for exercise. I have been doing this for almost 7 years though.

By the way, that 16 was probably a mistake. I’d remove it, as it’ll make the graph easier to follow.


My blood glucose (BG) goes up every time I exercise. I do mostly cardio, but I also lift. Something like 30-40 mg/dL up, whatever I do. It’s infuriating! I don’t measure ketones in my blood, but I suppose they’re going down if BG is going up.

Now many youtubers are posting continuous BG measurements and it seems most of them, if not all of them, have this “problem”.

I’ve also recently read about 4 “sub” types of diabetics and at least one of the “sub types” has BG raising after exercise, instead of decreasing. It must be terribly frustrating.

I’m not diabetic myself, but BG worries me.

(Old Baconian) #11

This may not be an accurate assumption. If your serum glucose is rising because of gluconeogenesis, then it is probably benign, because the same glucagon release that stimulates gluconeogenesis also stimulates ketogenesis. (Serum ketone levels probably drop because the circulating ketones are being used.) I suspect that the rise in serum glucose is an adaptation that allows the body to respond to the need for explosive power, and not something dire.

Remember that, since the α- and β-cells in the pancreas are intermingled, the levels of glucagon and insulin help regulate each other. The key is not so much the absolute level of either hormone, but the ratio of insulin to glucagon. When the ratio is low, catabolic processes predominate; when high, anabolic processes predominate.

The story is different, of course, when we eat carbohydrate, especially to excess.


Wow! So, it means when my BG goes up and I haven’t eaten carbs, so it’s gluconeogenesis, my ketogenesis is also high at that moment? Nice to know! I always thought that the unwanted BG raise could end up throwing me out of ketosis. I don’t have a blood ketone meter.

Do you know if the raise in ketones could be somewhat measured with a breathalyzer? I’ll test it from now on.

The morning gluconeogenesis then also means I’m more “ketogenic” at that moment?

Thank you for the info!

(Old Baconian) #13

Ketones may be lower after exercise, because you’ve been using them. You won’t know what’s going on in your particular body, till you can measure. But it’s a reasonable guess. Let me stress that this is speculation, but I believe it to be sound speculation. Be careful with breathalyser readings, because those are excreted ketones, and a lot of factors influence how much gets excreted and how much saved. (Don’t let an unexpected reading send you into a tailspin, in other words.) But if you are not eating carbohydrate, it is pretty much a given that if you are still alive, your liver is producing ketones.

(Bob M) #14

I’m not diabetic and have had a 2-hour Kraft test (both blood sugar and insulin) that was normal, and my blood sugar goes up during exercise. And I think that’s common.


Yes. Lots of people are like this. And yet, you read all over the web to exercise if your BG is high, to bring it down! Seriously??!

But for many people, it actually works.

With me, it raises. I’m not diabetic either.

Thank you for sharing! I love all the data you share in your posts and your help when I’m struggling to understand something. Much appreciated!

(Alpha Male) #16

Question during a fast in am from night before started around 8pm. Took ketone measurement 1.3. Me and wife went to hone depot I chewed this gum spry had xylitol got home was .3 than so I assume xylitol makes my insulin spike. Am I just way off or is that possible didn’t exert myself at all while we were out.
Thanks in advance if you could help. Learning🤦🏼‍♂️

(Old Baconian) #17

Your ketone level is variable, and not always because of insulin. Measuring blood ketones tells you the gap between production and consumption. So if your organs have been using ketones, your level will drop, and if your liver has been busy making ketones, the level will rise. The level of circulating ketones also depends on the kidneys’ ability to filter them out of urine and return them to the bloodstream.

While it is true that insulin inhibits ketogenesis, the only real way to tell if xylitol is affecting your insulin is to do a controlled experiment: take a glucose reading at baseline, chew some gum, and take glucose readings at 30, 60, 90, and 120 minutes. From the pattern of glucose readings, it is generally clear whether your insulin level was affected or not. Unfortunately, the insulin test is a radioassay, and no one has been able to develop a home testing method, so we can’t observe the effect on insulin directly.

While it can be helpful to measure serum ketones, there is no observed correlation between serum β-hydroxybutyrate level and the effects of being in ketosis (fat loss, HbA1C level, insulin resistance, etc.). Dr. Phinney has said that he and Prof. Volek picked 0.5 as the diagnostic level for nutritional ketosis because that’s where they saw the benefits in most of their research subjects. He says that 1.0 appears to be somewhat more beneficial than 0.5, but there appears to be no additional benefit from β-hydroxybutyrate readings above 1.0. And many of the elite keto-adapted athletes he and Prof. Volek have studied had β-hydroxybutyrate less than half of 0.5 and yet were still clearly in ketosis.

ETA: Bearing in mind that the mere thought of food can stimulate insulin secretion, I don’t think it’s too important to track all these numbers too closely. What matters is eating right, and observing the general trends of our measurements. The actual values are not so important.