Caffeine effect BG levels?

(Tony H) #1

Hi, Im new to keto but a few days ago upon rising I had a cup of tea, no sugar just a splash of semi skimmed milk. My blood glucose went from 4.4 to 5.6 within 20 mins so the next day I had tea with a splash of unsweetened almond milk which has zero carbs in it and the same thing happened. I assumed it was the semi skimmed milk but apparently not. Is this caffeine effect? If it is, I regularly drink anything from 4-8 cups a day so assuming this will cause me issues getting into ketosis and will have to go?

(Stickin' with mammoth) #3

The short answer is maybe, but there’s only one way to find out for sure.

Instead of going cold turkey, though, try switching to half-caff or drinking half as many cups or drinking them at different times of day. Try one change at a time and do it for a week or more to isolate its effects from any daily variables you might be experiencing. Then, see how you feel. Experiment with taking it alone, taking it with food, taking it after food, taking it with zero carb, etc.

Not all of us respond predictably to the established rules of keto, not even the scientifically tested results. Luckily, this kind of testing is free. You’ll figure something out, don’t worry.

(Robin) #4

I switched to decaf years ago, and no issues and learned to love it. I drink that any cups a day too. Worth a try.

(Tony H) #5

I switched to a decaf coffee this morning with a splash of almond milk and went from 5.3 to 5.6 so much better response. Think I’ll cut down and switch to decaf. I dont really consume it for the caffeine (that I know of) I just like a hot drink.

(A fool and his bacon are soon parted) #6

What always intrigues me about discussions of coffee and keto is that the discussion rarely centres on caffeine, only on coffee as a whole. Tea and caffeinated fizzy drinks never get mentioned in the discussion. And nobody will tell me why that is.

Also, if caffeine is having an effect on ketogenesis, then I would also expect other methylxanthines, such as the theobromine in chocolate and the aminophylline in certain bronchodilators, to also have an effect, but we never hear about those in the context of a ketogenic diet.

All that said, however, if you find you have an effect from drinking caffeine, then you should act accordingly, to get the results you want. I can believe there might be quite a range of individual variation in something like this. And as Richard Morris points out, while the Dudes’ first dogma is “Show me the science,” their second dogma is "Find what works for you."

(Stickin' with mammoth) #7

People might be automatically conflating the two but you’re right, it’s the caffeine that should get the side eye first.

How many people do you know who eat unsweetened chocolate? Hard to tell if it’s the theo or the buttload of sugar in that bon bon that’s throwing them off.

I gradually titrated the caffeinated beans down and the decaf beans up in my mix until I found the perfect mix: 1/3 caf. Every once in a while, I see if I can go lower. I sleep fine, so no worries either way. For me, it’s a mood enhancer. One strong (as in flavor) cup a day in the morning has been keeping depression at bay since the 90s. Just works like that for some people. Hella cheaper than Prozac, I hear.

BAM! (Emeril voice)

(Bob M) #8

I tested the effect of coffee and tea, on lipids and insulin:

I water-only fasted overnight, then got tested, then chugged coffee and tea, then got tested. As you can see, neither lipids nor insulin move much.

I did not test blood sugar, because way back when I was using pin-prick meters, I compared blood sugar before and after coffee, and my blood sugar went up. I delayed drinking coffee until after I tested multiple times. Guess what? My blood sugar went up.

The dreaded glucose sparing effect.

As a person who drinks coffee/tea only in the morning, I can’t really test coffee, as my blood sugar goes up in the morning regardless of what I’m doing (I don’t eat breakfast, which I think oddly would lower morning blood sugar).

It’s like testing whether alcohol causes a blood sugar drop. Since I drink only before bed, and my blood sugar is going down anyway, I can’t figure out whether alcohol has a similar effect.

(Robin) #9

I should note about my decaf intake…. I don’t measure a darn thing. Nada.
I have been coasting along for almost 2 years now, keto to carni. Weight and health are at optimum. But I couldn’t tell you about ketones etc. so, please don’t assume I have a medical opinion in any way.

I just love the taste of coffee.


Thanks for your data. And I think you’re right about “The dreaded glucose sparing effect.”

My guess. The increased level of ketones resulting from consumption of caffeine (and even more so when combined with something like MCT) lowers the use of glucose by muscles. Ketones are the preferred fuel - so the muscle cells use it first and block their glucose receptors while doing so. And BG goes up temporarily. I suspect this occurs whether or not you’re in ketosis; just probably moreso and more efficiently if you are.

My rationale. Caffeine stimulates ketogenesis - the links I posted above reference this, and anyone who cares to do a search will turn up hundreds of such articles and studies. If you combine the caffeine with MCT, another ketone booster, you get a synergistic effect - this is the science of ‘bulletproof coffee’. Both caffeine and MCT go straight to the liver and stimulate ketogenesis and lipolysis.

As noted above by @PaulL there is caffeine in lots of other beverages and a similar effect can be expected. In fact, many so-called ‘energy’ drinks contain not only caffeine but other stuff that stimuates ketogenesis - and/or cortisol and adrenaline.

(Bob M) #11

I think you’re incorrect, at least in my case. I’ve never seen blood sugar go up, and I wore a CGM for over 15 months.

Also, since starting a keto diet on 1/1/14, I gave up taking blood ketones when my levels hit 0.1 or 0.2 every day. If caffeine causes increased ketones, why did I never see this, even after years of taking ketones?

The only time my ketones increase now is if I fast multiple days. (There is a daily cycle that’s opposite to blood sugar: blood sugar goes up in the morning, down at night; ketones are lowest in the morning, and highest at night.)

I personally don’t think bulletproof coffee has any “science” behind it. For me, it’s a way to gain weight. Fat and I don’t get along. If there’s someone who feels better when drinking bulletproof coffee, or if it helps them, more power to them. But I found all it is, is extra calories.


The OP’s experience is your opposite. I don’t donate blood, but I drink ‘keto’ coffee each morning. That’s a mix of fats (including MCT) and protein (collagen and whey) to my macros. I also consume one or two ‘energy’ beverages during the day. None of this has caused me to gain any weight or change my body comp.

I think the ‘science’ of caffeine and MCT on ketogenesis is very convincing. I also suspect that the specifics of any individual result from multiple factors that would be difficult to control for.

(A fool and his bacon are soon parted) #13

And the cortisol and adrenaline also stimulate an increase in serum glucose.

(Stickin' with mammoth) #14

I blame college. I went in hating the taste and came out with a serious yen. I only drank a cup a day but, boy, was that cup loved. Higher learning.


Yes! As soon as I have the time I’m going to investigate the effect of the various ingredients of ‘energy drinks’ (taurine, ginseng, etc.) I’ll probably create a topic to discuss it.