Metformin and Type 1 Diabetes – An Experiment

Metformin is not usually prescribed for Type 1 diabetes, but over the past couple years, inspired in part by Mike’s experience on it (see here, here, here and here), I’ve become interested in trying it. Not only has it been in widespread use as a treatment for Type 2 diabetes since its approval in 1994, but it’s currently being investigated for potential cognitive and anti-cancer benefits as well. As Mike has asked, “Could metformin be the new aspirin?” 

The typical explanation for why metformin is not prescribed to people with Type 1 diabetes is that metformin increases your insulin sensitivity — and given that, by definition, people with Type 1 don’t make any insulin, it won’t help them. But I see two obvious holes in that logic. First, people with Type 1 diabetes do have insulin in their bodies; it’s just administered in a different way (i.e. injected subcutaneously, rather than secreted by the pancreas). And as anyone who’s struggled with the dawn phenomenon knows, people with Type 1 diabetes experience insulin resistance, too.

And second, metformin does more than just affect insulin sensitivity. It also appears to regulate the genes responsible for causing the liver to release glucose into your blood. As you may know, your pancreas and your liver work closely together to maintain a proper level of glucose in the blood. When you’ve got a lot of glucose in your blood, your pancreas secretes insulin to remove it (provided you don’t have Type 1 diabetes!). And when you don’t have sufficient external glucose – like when you’re sleeping — your liver releases some stored glucose so that your blood sugar does not drop too low. To put this a different way, insulin is what keeps a non-diabetic person’s blood glucose from getting too high; the liver (by releasing glucose stores when appropriate, triggered by the hormone glucagon) is what keeps a non-diabetic person’s blood sugar from going too low. 

I feel like I have an extremely overactive liver, which seems to take any excuse it can get to dump additional sugar into my blood stream, whether it’s needed or not. And I also seem to have difficulty absorbing the insulin delivered by my pump. So I was really excited when my doctor allowed me to start trying metformin a couple weeks ago.

When I picked up my first prescription, I decided to ask the pharmacist for some advice — namely, what sort of side effects I should watch out for, given that I’d read stories online about uncontrollable vomiting. But no, she said, in front of the group of people waiting behind me in line. The most frequent side effect is diarrhea.  That’s why they start you on a low dose. 

With that noted (both by me and my fellow shoppers), I went home and took a pill with dinner, and gave myself a bit less insulin than I’d normally take (since metformin increases insulin sensitivity it also comes with an increased risk of hypoglycemia for people taking artificial insulin — i.e. Type 1s; see below). Then I waited to see what would happen.

I’m happy to say that in terms of my pharmacist’s warnings I was lucky: no GI upset. And I’m even happier to say that starting with the very first dose, I began to notice a difference in my post-meal blood sugars. Not only did my blood sugar start to rise more slowly than normal after eating (which itself is fascinating — I’d always thought I absorbed food very quickly, but perhaps what’s really going on is that my liver is dumping glucose into my blood right after I eat), but the post-meal line on my Dexcom was much smoother than normal. 

I can’t remember what I ate for dinner the first two nights, but I can tell you this: my total daily insulin dropped from about 22 to 25 units per day to between 15 and 20. Considering that about 10 of those units are basal, that’s a really big reduction — in the most extreme case, we’re talking 5 units of bolus insulin per day. (Granted, I eat a very low-carb diet, but still.) I felt an eerie sense of ease — as if the metformin were somehow making my diabetes . . . dare I say it . . . simpler, and easier to control. It was an amazing feeling. 

That was about two weeks ago, and I’m now up to a full 1000 mg daily dose (in my case broken into twice daily 500 mg tablets). My past 5 days’ worth of totals (including basal insulin) are: 18.35u, 14.65u, 15.975u, 17u and 21.8u and my blood glucose hasn’t spiked above 200 mg/dl. (Again, I eat an extremely low-carb diet, am on a Dexcom CGM in addition to a pump, and am a wee bit obsessive — but even with all that, this is unusual for me.) When it comes to my own diabetes management, I am a Metformin believer. 

With that said, a major caveat: in addition to whatever it’s doing with my liver, the metformin also definitely increases my insulin sensitivity. I have had more lows these past two weeks than normal (which I figure is to be expected as I learn how to use it), and I have had to drop not just my mealtime boluses, but some of my basals as well. I do not recommend trying any of this without direct supervision or help from your diabetes doctor or endocrinologist, since the risk of hypoglycemia increases for people with Type 1 (it’s not a problem for people who are not on artificial insulin, which is why hypoglycemia is not typically an issue with metformin and non-insulin-taking Type 2s). In other words: this is not medical advice!

But with that said, I’m personally pretty excited. Stay tuned for further updates. And if you’ve had experience yourself with Metformin and Type 1, I’d love to hear about it in the comments section. 

Comments (8)

  1. I’ve been taking Metformin for close to 3 years now…I am Type 1, but over the years have become steadily more insulin resistant. I started out taking 2 per day, one in the morning and one at dinner, but was gradually able to wean down to just a morning dose. Taking Metformin has made the post-breakfast blood sugar spike almost non-existent, and really helps regulate my sugars all day long. I’ve noticed CRAZY things happen on the occasional day I might miss taking my Metformin – those are not fun days. I also credit Metformin with helping my PCOS, and actually helping me get pregnant 1 time….. I have a couple of blog entries about it – feel free to read up! :)

  2. Rhonda — thanks so much for your comment, and for the link to your blog. I just spent a bit reading your entries. Fascinating! 

  3. Very interesting, thanks!

    There is an error in the  second paragraph, where it says that “metformin reduces your insulin sensitivity”. That should say “increases”. 

  4. Mike f. at

    Ok I’m a type 1 on a Tslim pump with novolog.  my endo started my with Victoza and I hated the side effects. Then added 2000mg of metformin to the regime. 1000 at bfast and 1000at dinner. Works great. 

    Recently my though I’ve add invokana to the mix. 100mg at bfast. This combo has worked MIRACLES for me. I have literally not had a day where my BGs have gone over 180. But basals by 20%. 

    it is so effective that I had 4 slices of pepperoni lovers  pizza and my Dexcom didn’t budge. 

  5. Mike f. at

    Sorry typed that on iPhone. Should say cut my basals by 20%. 

  6. Nikke at

    For those with type 1 and  taking metformin are you taking extended release or immediate release? also are you noticing any benefits with weight loss after starting the metformin?  thanks for your input in advance. 

  7. I have type 1 diabetes and have used metformin successfully for several years now.  I did not tolerate it very well in the beginning, stomach upset and diarrhea, but after about a year was able to tolerate up to 2000 mg per day.  The dose that I take is variable and balanced with my food intake (type 1 is an exquisite balancing act).  I often take one 500 mg tab with small meals and 1000 mg with my largest meal.  I also find it to be particularly helpful in balancing the delayed effect of proteins and fats on glucose.  My favorite routine is a Jimmy Johns unwich for lunch, metformin, no bolus/rapid insulin and an afternoon at the pool with my family with no fear of low or high glucose!!  Metformin is not nearly as potent as some of the other agents mentioned in these comments, such as Victoza and Invokana which I have also used, and as such its (metform’s) effects can be overwhelmed by diets that are not moderate.  I am also an endocrinologist who specializes in type 1 and here is the thing about all of these non-insulin adjuvant agents that some of us are testing:  they can be helpful in many cases BUT you have to be very careful!  You cannot just add one of these agents into the mix and expect that it is going to magically stabilize glucose.  The reality is that it often adds to the glucose chaos until insulin doses are reduced in accordance with the effect seen from the adjuvant agent.  It does suppress my appetite a little and I have lost weight on it.  The insulin dose reductions can be tricky as there is a need to reduce insulin first due to the effect of the metformin and then as weight is lost.  I have used both immediate and extended release formulations and the difference is important in terms of how to adjust insulin.  If you are going to try it, you have to be ready to work hard as change is tricky in type 1 and you have to have a doc/team that is engaged and willing to work closely with you.  Take care!

  8. Mary at

    People taking metformin should be aware that B12 is one of the vitamins this drug depletes.
    Please either just supplement with methylcobalamin sublingual or have your doctor test for B12 levels.
    B12 is VERY hard to overdose on, so do some research and make your own decision.
    Dr. Hyla Cass has a book on Amazon called “Supplement Your Prescription” that lists several drugs and the various vitamins and minerals they deplete. It is a highly useful book since there ARE so many drugs in that category.

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