Thyroid and insulin

My T1 daughter was recently diagnosed with Hoshimots and prescribed Synthroid. She is very insulin resistant, (goes through about 200-300 units every 3 days) I was told the synthroid may help with her numbers. Anyone experience this? She’s been low the last two evenings and I’m wondering if it’s just a coincidence??

Hi aprilpls2, it is very possible that the thyroid medication has improved the bg. The thyroid is an important gland and when it isn’t working properly then the entire endocrine system can suffer. When the thyroid can function better it may increase the basal metabolic rate which would reduce the insulin needs.

Can you tell us how old is your daughter? Diabetes and Hypothyroid are both Auto Immune issues and the thyroid issue(s) often occur in PWD. Your daughter is going to feel better, her IR may improve, and many other health issues known or not may improve.

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I would not hold your breath on that.

Anything is possible.

I would consider it unlikely however.

What dosage synthroid are you starting with? For just starting out, 25 mcg is not uncommon.

One would assume you will be getting Thyroid labwork as a followup six weeks after starting the medication so as to confirm the correct dose?


I know several parents of children with both T1 & Hashi’s. None of them have mentioned levothyroxine (Synthroid) lowering BG. In fact, unexplained lows were one of the first symptoms of hypothyroidism. All have told me BGs increased after starting treatment.

From this article:

“In hypothyroidism, liver secretion of glycogen decreases, but so does degradation, leading to increased levels of glycogen. Absorption of glucose from the gastrointestinal tract is slowed, and glucose utilization is slowed in the peripheral tissues. The availability of gluconeogenic substrate is decreased. Additionally, the insulin half-life is prolonged, insulin levels are lower, and insulin secretion is reduced, which may lead to reduced insulin requirements. If exogenous insulin is not decreased, hypoglycemia may occur. It is likely that glucose levels will stabilize during hypothyroidism treatment. But when thyroid function is normalized, this may lead to higher blood glucose levels and adverse effects on glycemic control.”

Levothyroxine is also the list of meds that can raise BG found at

I am T2 & also have Hashi’s. I took Synthroid for several years. It did raise my BG. I didn’t make the connection until I switch to WP Thyroid (natural dessicated thyroid) last year. My BG returned to the levels I saw prior to starting Synthroid, so I’m not convinced the effects are entirely due to stabilized thyroid function.


For T1 it may reduce the insulin needs. If the OP daughter is experiencing hypo now, this could be just the beginning of improving the IR and reducing insulin needs. This was my own experience with levothyroxin though I was not a child and sans IR.

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No doubt it could be an individual response. My T1 daughter was dxd with Hashi’s in November (positive antibodies) but not yet on meds. She’s been experiencing the same unexplained lows other parents have mentioned, although shes no longer a child. It will be interesting to see how her BGs are affected by the meds.

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She is 12 years old. The resistance has been getting worse since at least the 2nd year. The amount of insulin she takes per day is really crazy. Her basals alone are over 50 units.

She has been started on 50. Yes they will be testing her again in 6 weeks. I’m doubtful it helped so fast. But hoping it will in the future.

This isn’t “crazy” depending on so many things. Hopefully the thyroid meds are going to give your daughter the improved metabolic function and so on as said earlier, and then the rest of the body follows like increased energy, less tired, not so hungry, etc.

IR is a worry for one so young, does she have a good diabetic team to help with managing her condition? I hope your daughter is on the way to feeling like a twelve year old with huge plans and goals. The better she feels, the better her condition can be managed!


I’m hoping for the same! It makes so much sense after reading more about it. Especially the hunger and weight issues. We have a lot of support and I’m so grateful for that. Thank you for your help!

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TD1, Hashimoto’s and celiac disease are strongly linked. About 6 % of TD1’s have celiac disease. Has your daughter been tested? Celiacs can be asymptomatic. Not everyone has the old classic GI symptoms. It can impact your blood sugars/control and food absorption.

I have Hashimoto’s and celiac disease. I am a TD2 (slender and in shape). I can tell you that I was asymptomatic when I received my celiac diagnosis. Please insist on a full panel and not just the screening TTG.

Celiac disease can develop at any time, so if she is negative now, be on the look-out in the future.

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How old was your daughter when dxd? 50u/per day basal for a 12 yr old girl isn’t unusual. Puberty & growth hormones cause IR.

Yes, she actually has been tested for Celiac, They performed an endoscopy and a colonoscopy on her last year. The Hashimoto diagnosis came after.

She was 6. She will be thirteen on thursday the 15th. This has been going on (with the insulin) since about year two of diagnosis.