Levothyroxine and Blood Sugar Levels

Hi there,

I am 34 weeks pregnant and was diagnosed with full blown Hypothyroidism a few days before I found out I was pregnant (my mum was also diagnosed in her late. 20s/early 30s so it made sense).

I have been on 50mcg of Levothyroxine throughout most of the pregnancy. I have had next to no advice on the side effects of this drug on pregnancy as the priority was always to get my levels sorted asap to avoid the usual risks associated with high THS in the first trimester.

The baby is now measuring large with cause for concern, and it's pointing to gestational diabetes. I don't fall into the risk category for this condition and have a very healthy diet so am wondering if there could be a link to raised blood sugar levels and Levothyroxine which is what I'm starting to suspect?

Any advice appreciated.

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  • I have a very healthy diet, exercise well & have never carried any weight. I have (very bad) gestational diabetes in all my pregnancies. There is a link between GD & an under active thyroid. (Though most docs don't seem to know this.) If you have GD & it is being untreated, this could cause your baby to be bigger. However, there are more signals of GD than this & you are showing other signs of GD, your midwives will test you for it. Have you been tested?/requested a test? Could just be that this is a bigger baby?

    Another thing you could do if you are worried, is monitor your own blood sugars. Phone the minister companies & they will send you a free one & then you will have to buy the tester strips. (They are expensive, about £20 for 2wks worth of strips. If your no's are high, you could take them to your midwife & use those to request a test. (However, you are so close to the end of your pregnancy, that there might not be time for all this!!!!)

    Ps. Levo/T4 will not harm the baby.

  • Thanks both, really useful. Had test for high blood sugars done today so will have a result tomorrow.

    I find it baffling that doctors don't highlight the connection between Levothyroxine and GD at the beginning of the pregnancy as it seems so common when I search online and blood sugar is even listed as once of the side effects of the drug.

    If so, I could have followed a low GI diet from the start and lowered the risks to both me and the baby. Possibly may have saved the NHS a chunk of cash too! Crazy.

    Thanks again.

  • Possibly, but unlikely if you already follow a good diet. If you follow a bad diet, then changes could be enough to sort out GD, but if you already follow a good diet, then it's likely you would need to be drug controlled at some point, once your body worked out that you were trying to be clever with your food! (I'm not on Levo, I'm on NDT.)

    Because you are so late into your pregnancy, if they say you have GD, it won't be too bad for you. It's likely you will control with diet, or diet & drugs, rather than ending up on insulin. (The body reacts well to each, but sometimes only for a while.Luckily for you, you only have "a while" till you give birth.) after my 1st pregnancy with GD, I get diagnosed early-at 4wks, so I am on insulin very early.

  • Thank you! It's so useful to hear someone else's experience. Based on symptoms I'm fairly sure it's GD, but it's just come on very late as you say, so not long to manage it!

    I was told to avoid NDT as I was pregnant and as newly diagnosed they (the consultants etc) wouldn't let me try it as they were worried about changes, but it's something I will be looking into as soon as I get back on my feet as it sounds so much better.

    Thanks again!

  • They are frightened of using T3 in pregnancy because they don't know anything about it.....

    Let us know the results of your GTT test...

  • Hi,

    Hypothyroidism can cause diabetes even if you are taking medication because the thyroid gland is responsible for metabolism and the diabetes is a metabolic disorder. If you've got raised blood sugars then you are likely to have a large birth weight baby. Perhaps you need to have your thyroid blood test done again to see if perhaps you need a higher dose of Levothyroxine.

    I hope this information helps but you are welcome to PM me should you need to.

    Take care.

    TT x

  • Thanks both, really useful. Had test for high blood sugars done today so will have a result tomorrow.

    I find it baffling that doctors don't highlight the connection between Levothyroxine and GD at the beginning of the pregnancy as it seems so common when I search online and blood sugar is even listed as once of the side effects of the drug.

    If so, I could have followed a low GI diet from the start and lowered the risks to both me and the baby. Possibly may have saved the NHS a chunk of cash too! Crazy.

    Thanks again.

  • Hi,

    Have been taking Levothyroxine for two weeks due to hypothyroidism and have type I diabetes.

    I am usually really, really well controlled and have found that since starting the drug my blood glucose control has been much harder with dramatic swings both up and down.

    Not sure of the biochemistry as to why as insulin is a peptide hormone but that is what has been happening to me.

    Definitely helped by low Glycaemic Load diet.

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