Is it okay to use metformin while you are on an insulin pump and CGM?

I used to be on metformin as well as glyburide and Januvia. However,at some point, my blood glucoses started to be really high and doctor started me on Humalog 75/25, plus the above meds. Started seeing an endocrinologist at the suggestion of my PCP, who did a blood test which showed that my pancreas had pretty much stopped working at all, thus according to him, moving me from a Type 2 to a Type 1. He told me to discontinue all the pills, and ordered me an insulin pump (Medtronic Mini-Med 530G) with continuous glucose monitor. During the last five months with the insulin only, my blood sugars have been extremely high and extremely low, and I have been very unhappy with the way things are going. My endo had made a couple of changes to my pump settings, but then he told me that I was obviously "eating way too many carbs" and should go on more of a low carb diet. Things did not really improve, however. Then I did something on my own, for which I was sure I would quickly die, or at least get very sick: I took one metformin, 1000 mg tablet. Previously, I was taking 1000 mg of metformin morning and evening. After two days of taking 1000 mg a day, I noticed that my blood glucose readings were staying more within normal range! Could this be the result of metformin? That is the only thing that I did differently. The last three or four days, I have been amazed at how much less insulin I have had to bolus, and it is so exciting to see the graph on the CGM registering a steady line which is just a little over 100 or under 100 for most of the day. It used to go way up and way down all day and night long. Is this to be expected or am I wrong to associate the metformin plus Humalog insulin with much better results?

I think so! Here is an article from the fabulous Amy Tenderich (AmyT) over at DiabetesMine over 4 years ago that discusses it.

From what you describe, it sounds like the Metformin is helping. Strictly speaking, you didn't move from T2 to T1. Either one of two things happened: As a T2 you sustained significant pancreatic strain through sustained high blood sugars that you eventually burned out most of your beta cells, or you were misdiagnosed as a T2 when you were actually a T1 LADA (this is not uncommon, unfortunately) and your autoimmune response finally reached a point in destroying the overwhelming majority of your beta cells.

In either scenario, it is not uncommon to also experience some insulin resistance. It seems that the Metformin is helping with that and/or moderating glucose release from your liver. As such, I would continue using it. Many T1's use it quite successfully, including myself. It will increase your insulin sensitivity (as you've witnessed so far), so be sure to keep a close eye on your pump settings and turn them down accordingly.

Good diabetes management is all about trial and error, and everyone's diabetes is different. Great job in discovering this on your own!

I failed to notice you said you were using Glyburide when I read your post the first time. Unfortunately, one of the side effects of long term use of this and other Sulfonylurea class drugs can be beta cell burnout. This might have been what happened in your case.

Thanks, Christopher! WOW--I am so glad to read all of the posts that have been addresed to my question! First of all, in my original post, I was just quoting what my endocrinologist told me, about my "pancreas being totally useless now". I had also been on Metformin, first as Glucophage, later Avandamet, and finally just Metformin by itself, plus the other two pills. Over several years, I became anemic, lost a lot of weight, and after having open heart surgery in 2012 was so sick from not being able to eat because I had no appetite, that I finally stopped taking Metformin altogether. I got much better, and now feel really good, except I have gained about 15 lbs and am noticing that my clothes (which I had to buy a whole new wardrobe), are now becoming too tight. The doctor took me off of glyburide and Januvia and just put me on Humalog insulin with my pump. He does not know that I have started back on Metformin...but it sounds like he might approve. My PCP had told me before I got the pump that if I started gaining weight after going on the insulin pump, that "you can always go back on Metformin", so that is why I did just that. I agree with some of the other posters, it does affect my low blood sugars, by it taking much longer to recover--I'm seeing the endo doctor soon and hopefully he can help me adjust my setting of the pump. I have never changed anything on my own--he's the expert and I would not want to screw things up when I don't understand what I'm doing. Thanks again for your answer!PS--I have heard of having a Glucagon pen to keep on hand, but no doctor has ever prescribed one for me--will have to do that soon. Also, what does LADA mean?

Hey Sandy. It sounds like you've been on quite a journey, but making progress too. You are wise to get a Glucagon emergency kit. I have several in the house and always carry one in my briefcase. What's also important is to have glucose tablets and/or glucose liquid to treat lows quickly. Apologies for the acronym. LADA stands for Latent Autoimmune Diabetes of Adults. You can read more about it here:

Hi Sandy. I strongly encourage you to get the book Pumping Insulin by John Walsh. I understand your reluctance to change things without your doctor's help, but most of us do find in time that it's easier to make changes on our own and not have to wait for doctors appointments each time we want to tweak a dose.

Sandy, I am you.

T2, pump (Omnipod), CGM (Dexcom G4).

I take metformin. 1000mg, 2x a day. It makes an enormous difference in the ability to control my BG effectively with insulin. I can do it without the metformin, but the volatility is much worse, so I have to "do" a lot more to maintain tight control.

Without metformin, I'm correcting, correcting, correcting all day. With it, I can rely on my IC and other parameters to get predictable results bolusing, and pre-bolus timing to keep a lid on postprandial spikes is much more predictable.

So, from a practical treatment sense, there is no reason arguing against metformin and insulin together, if it improves one's treatment outcome.

In a pharmacological sense, there is no issue really either. Adding exogenous insulin from the body's perspective looks no different than the native stuff. It can't tell you injected it rather than produced it (for the most part -- there are rare people who react badly to the insulin analogs, and have to use regular Humulin).

Finally, and this is really important, you really need to take control and be the "expert" in managing your diabetes, rather than be dependent on your physician to manage it. This means learning all about how the pump works, what all the settings do, how they relate to BG levels and your body's reaction to insulin, etc.

You must get up to speed enough to confidently make adjustments to your pump at any time, any day, without having to consult your doc. Keep them in the loop, yeah. But you've got to own this.

TuD is an incredible resource for getting yourself to that point. Almost all of the pump-using diabetics here are virtually self-sufficient in controlling their pump, and most of us are constantly fiddling, tweaking, creating additional basal programs for different situations (like having a cold), etc.

It seems overwhelming, and like a ton of work to listen to it described. Have faith -- like just about anything, once you're up to speed, it's easy. In fact, most of us find that, once we've become our own expert on this, managing D with a pump is much easier than without.

Excellent advice Zoe and Dave. I couldn't agree more.

Thank you Dave, Christopher and Zoe! I will check out the Pumping Insulin book as soon as I can. And I am SO encouraged by reading all the posts about using Metformin with insulin!! I had no idea that it was possible, and was wondering if I should tell my endo next time I see him. By the way, the reason I came off sounding so dependent on my doctor was that both he and the customer support people at Medtronic, as well as my "trainer" emphasized over and over that I should NEVER make any changes that are not initiated and instructed by my doctor. I went back on the Metformin on my own,with great fear, and feel so thrilled by the positive results in just the few days since I did. I do have questions about how to manage the settings on my pump, but will definitely get down to work learning more by browsing this wonderful forum and interacting with all of you (new) friends. Thanks again.

Sandy, they're treating you like an idiot, and it's clear to me you're not :-)

Be polite, civil, friendly, but firm that you want to take full control of your treatment, with their support.

If they will not get on board (ever), you need a different team. They may be nice people, but we're not playing bean-bag here.

That said, I'd be surprised if they wouldn't work with and support you taking more control yourself. It makes their job easier.

I can't imagine not being able to adjust my settings (like changing which basal program) on my own. I know my control would be much worse.

Best of luck, and I'm really eager to see that post from you in the near future, "I'm figuring out my basal, I have it set X from 7am to 10am, Y from blah to blah, blah blah blah". That'll be a sweet post!

Thanks again for your support and helpful advice. I'll do the education and then let y'all know what I've changed. I am so excited! I was getting discouraged because I didn't think it was allowed to mess with my settings, but now I am going to be my own advocate in my care. I also want to get the book (Pumping Insulin)that Zoe recommended ASAP.

Zoe, I am about to order a book, probably the Pumping Insulin one, from that you recommended. However, I read some of the reviews for the newest edition (2012) and am wondering if the information in the book will be pertinent to my brand new pump (Medtronic 530-G) and CGM (Enlite), since they were not on the market before September, 2013. Will the book be worth purchasing even if it does not mention my particular pump/sensor? Have you read the book "Live Like a Pancreas)(I think that is what it is called)? I'd love to get them both, but have to choose one or the other. Also, is your copy an actual book or do you have it on Kindle?

Hi Sandy
While I have not read "Pumping insulin" by myself, I think that book is more like an overview over how to use a pump and therefore not written for a specific pump. If you wanna learn the functions of your pump in detail, you still need to read the pump manual.
I can not tell what book to buy, the books are both great for sure, the author of "think like a pancreas" is great, he has been in videochats here often:
And here his "diabetes confession":

Maybe I could help a bit with the decision, but i hope Zoe can answer your questions better and more accurate ;)
Good luck

The 1st thing I noticed was that you use 75/25 insulin. Aren't you suppose to use fast acting insulin in your pump. I just want to tell you that I take Janumet 50/1000, and I'm on an insulin pump, and CGM. I like the pump, and have gone to a 6.4 A1C. I am still working on my control, and even with the CGM I still use about the same amount of testing strips as before. I have never seen an endo before, and have been a diabetic since 1995.

Be sure and come back here liberally to ask questions and get advice. TuD was indispensable in learning everything I needed to know to be totally confident in managing my devices!

Crowbird raises a good point. I assumed once you moved to a pump you moved away from the 75/25 Humalog mix. If you haven't, this can also create issues in trying to achieve good control with a pump. You want to make sure you're using a straight analog (no mix) with your pump: Humalog, Novolog or Apidra, for example.

Christopher and Crowbird: To make myself clear, i started out on pills only (in the 80's when first diagnosed with T2). I was very overweight at that time and eventually had to go on insulin only (don't remember what kind) I actually got to the point where I was injecting 60U morning and 60U night. Then I lost about 75 lbs over a five year period and did not need insulin any more, just oral meds. Then, over the last five or so years, I lost my appetite, became very anemic with iron deficiency anemia, and my doctor (PCP) put me on an insulin Kwik pen, using humalog 75/25, just for when my blood glucose went over 200. In 2012 I was diagnosed with aortic valve stenosis and underwent open heart surgery in December, which was hard to recover from....had all kinds of bad side effects from Plavix, amiodarone, lisinopril, and I thought, Metformin. I also had some serious complications from the heart-lung machine, A-Fib and low blood pressure. Under dr. supervision, I got off all of the heavy duty meds, and eventually started feeling so much better. Still took two oral meds, glyburide and Januvia. When I started going to an endocrinologist, he immediately did the blood test that measures how your pancreas is doing, and that's when he said I had changed from T1 to T2 and to just stop the glyburide and Januvia. I had already stopped the Metformin, thinking it was contributing to my inability to eat and stomach pain. I was so sad, because when using Metformin my blood sugars had been doing so much better and my A1C was always in the 6-7 range, and since stopping the Metformin that had increased to 8-10. Sorry if this is being repetitious! So now, about one year later, I am learning how to use an insulin pump and CGM, and not doing very well, until just about four days ago, when I tested taking Metformin again, and have now started achieving much more stable results. Yay! Now I am on Humalog fast acting insulin via the pump vs injections from Humalog 75/25 insulin via Kwik-Pen. Things are starting to look up, and I want to learn about how to do my own changes to my pump settings. Can't wait to get my Pumping Insulin book!

Hi, I am on the insulin pump and I take 1000 mg of metformin twice a day. All prescribed by my doctor.