Does caffeine affect for your blood glucose levels?

Diagnosed type 2 last September. Since then I have managed to excellently control my blood glucose through a fairly strict lowcarb diet (avg 35g per meal), gym/cardio 3-4 times a week (afternoon or evening), and daily Jardiance 25mg. (And of course regular visits with my GP and clinical pharmacist.)

So the last two days I’ve had unusual lows about two hours after breakfast, readings 65-70 with all the physical symptoms (shaky, sweating, irritable, etc.) I haven’t changed my meal plan, meal times or portion sizes, I haven’t changed my exercise or medication routine. The only difference is a new brand of coffee I started drinking yesterday. I’m not a big coffee drinker, typically no more than a single cup per day in the morning, if that.

I can’t imagine what else besides the coffee would be causing the lows? Does caffeine really have that much of an effect on glucose levels? If so, why is it just happening now, why hasn’t caffeine had this effect on me before? Am I on the right track thinking it’s the caffeine?

I find the opposite—caffeine/coffee tends to spike my blood sugar, if I have more than my usual amount, presumably due to cortisol release. There’s no mechanism I’m aware of through which it should lower blood sugar…

That said, the effects of caffeine can feel subjectively a lot like a low—I’ve definitely felt like I was low (when I wasn’t) when overcaffeinated. Same thing when highly anxious or otherwise having sympathetic nervous system arousal. Is it possible that your blood sugar is usually around that level (and maybe flat and fine there), but you’re not typically testing because you’re not feeling off?

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My fasting reading (when I wake up) is usually in the upper 90s, and typically goes up from there after a meal. My fasting reading is usually the lowest of the day, that’s why it seems weird that I would have such low readings late morning a couple of hours after I eat breakfast.

It doesn’t affect me at all. I drink 1-2 pots/day.

OTOH - anything white - bread, spaghetti, potatoes - I can’t get/keep my bs under control. So I no longer have them.

I have a can of bean sprouts as a sub for spaghetti. I microwave it long enough to dehydrate it to spaghetti consistency. Add spaghetti sauce and it’s close enough to satisfy any spaghetti cravings I have. Low carb, too!

Actually, this sounds more like reactive hypoglycemia. Do you have carbs for breakfast? You can check by having a really low carb breakfast like eggs and sausage and seeing if you have the same effect.


Brian had a great response…

I gave up coffee…not caffeine…because every cup required an insulin dose, usually 1u.

I now caffeinate with a green/black iced tea. Delicious, antioxidants, healthy, and no coffee breath. No BG rise at all.

The nutritionist I see has gotten me into the habit of keeping the number of carbs per meal consistent for every meal. So I do typically eat carbs at breakfast, but no more than any other meal. The hypos I’ve been having are only after breakfast though. Today I’m trying no caffeine to see if that has any effect, and tomorrow I will try super low carb. I see my GP next week so I’ll discuss with him as well.

I’m going without caffeine to see if that has any effect.

I haven’t had pasta in months, bread very rarely. 30-35 carbs per meal. The sprouts idea sounds interesting. We’ve been making good use of our spiralizer also.

(off topic here, but…)

@GenieInABottleRN have you tried spaghetti squash or Shirataki noodles?

@Warrenz1963 do you have any recipes using your spiralizer? We have more than a handful of members who like theirs - post them here

I’m always looking for new recipes!

No, but that’s a Great Idea! I use a can of bean sprouts, dehydrate in microwave to spaghetti consistency and add spaghetti sauce. Can’t tell the difference!

But TY again, @MarieB for even more great ideas
You’re the BEST!!!

So, a couple of things to bear in mind. First, most of us (maybe all of us) are more insulin resistant in the morning than the evening, plus we get a nice glycogen dump from the liver (also called Dawn Phenomenon). This combination means that the same amount of carbs eaten for breakfast are likely to have a much larger effect on BG than that amount eaten for lunch or dinner (especially if you’ve already exercised that day). Second, most non insuline-dependent Type 2s still produce significant amounts of endogenous insulin in response to eating carbs.

Put those together, and that is a perfect prescription for what Brian brought up: reactive hypoglycemia. That doesn’t mean what is happening to you is RH, but if I were a betting man I’d put money on it. Do the coffee experiment, by all means. But definitely try Brian’s suggestion as well (skipping 35 g of carbs at breakfast certainly can’t do you any harm): try eating eggs and cheese or whatever else works, but keep breakfast to less than 5 g of carbs for a few days. Don’t do it at the same time as the coffee experiment (confounding effects), but do it after you’ve satisfied your curiosity on that front.

As for the original question, the answer for me is “No, coffee doesn’t affect my BG one way or the other,” although the milk I sometimes put in it can.

To expand on my “carbs at different times of the day” thought, my own experience is pretty straightforward:

I generally have less than 10g of carbs before noon. I’ll often have 30g for lunch, and 60g for snacks and dinner (usually after I’ve worked out or done a lot of walking). For some reason that 10-30-60 distribution means most days my BG is pretty flat from fasting through the day, with my lowest point usually coming before dinner. Everyone is different, but my pattern isn’t particularly unusual I don’t think. It has to do with glycogen storage in the liver, the way muscles use glucose after even moderate exercise, and etc.

We have a few cookbooks we’ve picked up. Can’t say I have a favorite.

Thanks for the good info. I see my GP and clinical pharmacist next week, I’ll ask them about RH.