Does Metformin work for Type 1's?

Specifically, does it decrease the amount of insulin you take? I am wondering, because my Endo. thinks it’s pointless for me to try it, but won’t okay my taking Invokanna. So, if I can explain that it might help reduce my insulin needs, and therefore help me shed the few pounds I’ve gained in the last little while here while my insulin needs have increased, that would be great!

Any advice on how to convince my doctor? LOL And, please let me know if you decreased your insulin needs (type 1) with this medication.

Also, is this okay to take with a low carb diet??

There is a (glacially) growing awareness that T1s can indeed benefit from Metformin.

Metformin has two main effects. The secondary effect is to increase insulin sensitivity slightly. For some T1s that doesn’t mean much; but for others, it can, because there is also a growing awareness that it is possible to have both T1 and some degree of insulin resistance at the same time, and that a subset of T1s do.

But Metformin’s principal effect is to suppress the release of glucose by the liver. Less glucose in the blood equals less insulin required to control it. For most T1s the difference is not a dramatic one, but it does exist.

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I definitely use less basal insulin being on metformin but it doesn’t help with mealtime issues like spiking. I did lose a good bit of weight, though I think too much. Sometimes I think it affects (decreases) my energy reserves too, so that I trend low during exercise. So…pros and cons. BTW, I did experience a lot of GI symptoms titrating up to a full dose. :worried:

I am on Metformin. It took a while to find the right dose, but, yes, it did finally lower my insulin needs and I am beginning to lose weight.

My endo started me on it about 10 years ago to help with dawn phenomenon. I was on Lantus/Novlog MDI and the Lantus just wasn’t cutting it. Not sure why he didn’t recommend doing multiple Lantus shots the way some people do, but anyway it seemed to help and I’m still taking it even though I’m on a pump now.

Hi @Rose_Rose,

It is very common for knowledgeable and experienced endos to prescribe metformin and Invokana for type 1’s. I am a type 1 and I was on Invokana for 6 months. Then my a1c was so low, my fertility increased and I got pregnant. That’s the only reason I’m not on it anymore. I would still be on it if I didn’t get pregnant. I had fantastic results on Invokana so have some on the forum here. I had labs pulled for kidney, CBC, thyroid, A1c and lipid and they were markedly better after 3 months of med usage.
I reduced my insulin, carb ratios, and basal settings. I lost 25 lbs and my a1c went from 7.9 to 7.0.

I have little tolerance for ignorance in my doctors. Plenty, plenty of endo’s let their type 1 patients on Metformin and Invokana. The way the medication work shouldn’t really affect type 1’s any differently than type 2’s except in the event that there are prior kidney and heart issues for invokana. Same precautions apply to type 1’s as type 2’s. If I were you, I would go look for a second opinion from another endo. Potentially move to another endo.

Best wishes on your search,


My endo initially prescribed Invokana, which I was on for about 8 months. The pros were that it immediately reduced my insulin needs by about 25% and I lost about 15 pounds quickly and maintained. I was able to tolerate the slightly more frequent urination, but there were some more significant cons which swayed me to discontinue. I experienced pretty severe dehydration the extent that I would wake up several times a night with dry mouth and had to drink lots of water. Not that I drink alcohol excessively, but I could not drink more than 1 glass of wine because the combination of Invokana and alcohol exacerbated the dehydration to the extent that it was intolerable. Most importantly it caused me to have moderate ketones twice despite BGs in the low 100s. This is what the FDA warns against. I did not go into DKA, but did have to call out sick from work for the first time ever related to T1D in order to monitor and I felt like crap. After the second time, I decided to stop Invokana.

Then my endo prescribed Metformin, which I love! My insulin needs slightly increased from the Invokana, but still an overall decrease of about 15-20%. I gained some weight back while titrating, but have been able to lose it and maintain the 15lb weight loss. I think the best part is that it really helps control my appetite. I have had T1D since I was 5 (the Lente/NPH/R days, prior to fast acting insulin and MDI) and as a result believe that my brain/body never developed hunger/satiety cues. That’s another topic, but it is very satisfying to be able eat when I’m hungry and stop when I’m full. I did experience GI symptoms while titrating, but it was tolerable. I also follow a low carb diet most of the time.

My endo was very open to trying both, which I am thankful for. I would also agree that you might consider changing endos. Happy to answer additional questions.

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I am type 1, wear a pump, and take 2,000 mg Metformin a day. It seems to keep my sugars more level and stop sudden spikes. In other words, it makes the basal rates work harder.

Thanks for all the replies. Now I have some arguments to go to my Endo with! I’ll let you all know how it goes…

Precisely. Basal insulin is meant to manage the steady drip of glucose produced by the liver between meals. Metformin acts to control the same thing. My TDD of basal is a mere 7 units, and I have no doubt whatever that the Metformin is a contributing factor.

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only 7 units a day from basal?! that’s insane. i pump nearly 70 units a day from basal alone. what is your secret? is mine higher maybe because of psych meds?

No secrets here, but the following all contribute to reducing the need:

  • I am T2 with a small trace of beta cell function still remaining (0.3 c-pep, last time we checked)
  • I am not overweight and have very little insulin resistance to speak of
  • I follow a fairly strict LCHF diet

But the most important part of the explanation is simply that every individual varies from every other individual. My physiology is different from my wife’s, my neighbor’s, yours, and the others who have posted in this thread. What matters is not how you compare to someone else. What matters is doing what you need to do to have good control. Eyes on the prize—not on someone else’s race.