T1 and thyroid drugs

Hello guys! greetings from Brazil.
I guess this is my first post.
I have diabetes (T1) for the last 17 years and currently I am on a pump and have been using Dexcom as well.
Always had good control and could manage my weight pretty well…
2 years ago I did a check-up and found that my TSH was high - the doc started with levothyroxine 25mcg/day.
After 3 weeks he increase the dose to 50mcg. At that point my bgs started to climb… It was very hard to keep the BG under control. I had to adjust the basal in 30-40% and my carb/insulin ratio changed as well.

After living some months like that and injecting 40-50% more insulin, as expected, I started to gain weight.
For weeks, I would run every day, eat a minimum amount of carbs / calories and still would not loose weight.
I talked again to the doctor and she decided to prescribe metformin.
After taking Metformin my life became way easier. I could reduce the basal even lower than pre-levo days.
Now I can control my weight in a good manner again.

I have read in so many places the interactions between levo and insulin/ bgs. Most of the people says that levo does not affect their BG or in some cases it affects BGs while you are not in the right dose.
My dose keeps going up (today I am on 100mcg) and my TSH around 4.

Can you please share you experience? I would like to eventually stop taking Metformin, but today I cannot do that at the expense of gaining a lot of weight.


Hi! I do not have TD1, but I am a TD2 (not on insulin, so I will let someone else address that). I do have celiac disease and Hashimoto’s Thyroiditis. If you have hypothyroidism and Hashimoto’s is the cause (thyroid antibodies elevated), you might be experiencing thyroid flares causing your hormone replacement needs to fluctuate (you can swing from being hyper to hypo and that can drive both you and your doctor crazy trying to get a correct dose). Being hypo can cause weight gain and can affect your blood sugar management. It affects everything it seems. TD1, celiac disease and Hashimoto’s share a genetic factor (Google it.) As time goes on, your thyroid will probably stablize, along with your dosage, once a flare is over. If you also happen to have celiac disease too, you might not absorb your thyroid medication making you hypo again. So, it can be several things. Consider ruling out celiac disease and Hashimoto’s by getting your antibodies tested. Do some research on both theses conditions. These can develop at anytime during your life.

I would be tired if my TSH was at a 4, but it might be fine for you. Try to get it closer to a 1 without going hyper.

I hope you figure it out. :smile:

I have the same problem as you, Type 1 with Hashimoto’s Thyroiditis. I take name brand Synthroid for the thyroid condition and also Metformin because my metabolism is kind of sluggish. I decided a while ago that I want to continue taking Metformin because of the reasons you stated. I do exercise and watch my carbs, especially in the morning because that is when I seem to suffer the most from insulin resistance. If it weren’t for the Metformin, I’m sure my insulin requirements would go up and cause me to gain weight. Now, I’m maintaining a normal weight. If you are getting good results with the Metformin, why would you want to stop taking it?

I’m curious what dose of Metformin you are on with your Type 1.

I’m taking 500mg twice daily


not sure about the long term complications… now the doc put me on Sitagliptin + Metformin.
The only difference that I notice compared to Metformin alone is specifically when I exercise.
Before Sitagliptin, I would eat some carbs and wait my BG reach 200 and then start running on the treadmill.
After 45 minutes, my BG would be at 100… The problem was that after the exercise session, my BG would rapidly raise to 250+… so I needed to take a correction bolus as soon as I stopped running. Sitagliptin seemed to help a lot on that… now it does raise after the exercise, but it will stop raising at 170-180… that is the only difference that I noticed…

I’ve been taking Metformin for a couple of years and haven’t had any complications from it. I heard that it can deplete your vitamin b12 levels, so I take a supplement. I’ve heard that it can be hard on your liver. I think it’s one of those drugs that the benefit outweighs the risk, because I would probably struggle to maintain a normal weight and blood sugars without it. I already exercise and watch what I eat so there’s not much more that I could do. I don’t know about Sitagliptin; I’ve never heard of that drug.
As far as the blood sugar spikes do you take your insulin and eat right away? I know if I did that, especially in the morning I would get a big spike afterwards too. I wait about 20-30 minutes in the morning after I take my insulin before I start eating and that usually prevents a big spike. Maybe you are already doing this? I just know for me that timing makes a big difference. For lunch and dinner I wait 15 minutes before eating. Sometimes I take a little more insulin than I think I’ll need for breakfast and then a couple hours later I’ll make sure to eat a small snack, usually a small piece of fruit before my blood sugar drops too low. I know how difficult it is once your thyroid starts acting up but I’m sure in time you’ll figure out what works for you.

You may need t3. I have Hashimotos and I’ve started t3 as well as Levo. I still have a lot of symptoms but some improvement. My t3 was low so I’m not converting t4. With hashis you tend to bounce around from hypo to hyper so it’s harder to treat. My bg is better so far on t3 though. I have other stuff going on too.

You should get antibody tests done. My last TSH was 4.26 in the late morning. You should test in the early morning. Keeping Tsh at 1 or below can help stop antibody attacks.

I’m thin and have not gained weight so far from this. My father has hashis too and is also thin.

I have been on that same dose for a full year and it did nothing. I have asked to go up to 1000 mg twice a day. I’m hoping that will work.

Do you exercise? The Metformin does not work all by itself for me without exercising. I use an elliptical machine for about 40-45 minutes a day. If for some reason I can’t exercise, I lower the amount of carbs that I eat for that day.

I’m a walker. I walk every day.

Walking is one of the best exercises you could do. The doctor will probably have to adjust your meds. Another thing you could look into is ketogenic or low-carb dieting. A popular book that is always talked about on these boards in Dr. Bernstein’s Diabetic Solution. Some people swear by this method, but personally it didn’t work for me because I feel it is too restrictive and I felt deprived on it. Most of the time I like to eat at least 30-45 carbs per meal and I like foods like bread and potatoes although I don’t eat much. I guess it depends on your food preferences as to whether low carb dieting is right for you.