Thyroid UK
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Hypo and Type 2 diabetes

Does any know if poor treatment for thyroid can cause blood sugar to run high? I have both Hypothyroidism and now Type 2 Diabetes. Recently been feeing very tired and achy. Blood sugars in the morning in the low 10s which is quite high for me. I take 175mcg levo and 3x500mg metformin. My B12 was 218 range 150-900 so taking Boost a spray supplement. Any advice as to what to do? GP wont give B12 treatment as says in normal range.

9 Replies

Your B12 is far too low, no matter what your GP says. If you supplement it should be with methylcobalomin B12 and you can buy sublingual which goes into your bloodstream. I get mine from Amazon. You cannot overdose as excess is excreted. You should aim to be more than 500.

This is a link re diabetes. Some of the links within may not work as the site is archived.


I have found Boost oral spray which contains Methylcobalamin B12 and chromium. 4 sprays contains 1200yg. Not sure if it's helping. My daughter who is also a hypo has just been diagnosed with pernicious anaemia and my dad had it.


Well that makes it even more likely that you have PA. Your GP should be testing you for this properly (anti-intrinsic factor / anti-parietal cells) given the family history and the fact that you already have autoimmune disease. I hope you can maybe come by the Facebook page or the PAS forum for more advice. H x


So your B12 is already on the floor, and you've now been prescribed metformin, a drug that is well known to deplete vitamin B12. One can only despair at this kind of thing. Here is a link to lots of B12 info:

There's a Facebook Group if you wanted further advice:

Most people with a B12 deficiency use supplements to fill the gaps between injections, it is rare to find people who can get relief from supplements alone (although there are some). And you scupper your chances of getting a proper diagnosis as well, because supplements will raise your serum B12 levels but this won't always get through to the tissues and cells where it's needed. This is why some people with this disorder need to maintain levels in the 1000s before they feel well.

Serum B12 is a useless test to start off with, it's even more irrelevant once you are on injections or supplements. The commonly quoted ideal level of over 500 is based on someone walking in off the street and having a B12 test done, it's not meant to be a target to aim for once on treatment.

For what it's worth, a warning about the test's unreliability is here, this is an official warning that all doctor's should be aware of (or made aware of):

There are some shocking statistics behind this warning that I posted the other day:

"assay failure rates are 22 to 35%"



The lnk between type 2 diabetes and thyroid disease, is simply that Diabetes is autoimmune and hormonal. Once you have 1 autoimmune conditions, as my Hepatologist puts it " They like to hang around together" They appear gradually, so watch out for them. I have 12 at the last count, some more serious than others. The Diabetes diet is the best for thyroid disease any way.Metformin is very good, the one diabetes drug that does not caujse weight gain. Be sure to start with to do your BM, two hours after eating anything and befolre meals, last thing at night ( plus first thing). You will gradually understand your body and the glucose levels and what is best not to eat. Eventually, testing 3 times a day is fine. look after your feet, no cuts etc, eye check annually, not many opticians do the diabetes eye test, so ask,The best venous blood test is Hb1Ac.


If you want more info, click on "reply to this" under my post.


I believe that I have diabetes because of having hypoT. I've been told it wont go away because I wasn't obese when it started but will get worse over time. I already have background retinopathy but cant seem to get my blood sugars down at the moment and weight is creeping up again. Just thinking that if T4 to T3 change is poor this could have an impact on insulin resistance or production.


Hi Obese does not necessary follow with type 2. I am very underweight, to all my consultants despair ( not mine!)My diabetes is very bad, so bad that I also have Peripheral Neuropathy, which is worse.If seeing a general Endo, they are best placed to look after your diabetes.Make sure the Metformin is slow release, there are 2.forms of it.

Thyroid, the first choice by most Endos is T4 ( levo) and T3, but before that essential to have TSH, T4 and Free T3 tested, and 6 weeks after treatment alters too. FT3 over range is dangerous. With Diabetes you also need to take extra care of the heart and kidneys.Ideally 6 monthly U`s and E`s ( renal function).I had thyroid disease, 30 years before developing Diabetes. Also I was very fussy to never , ever , eat any thing "bad".

I hope that helps,



yes thanks Jackie. From earlier posts is it best not to take B12 and multivit substitutes and let symptoms get worse for a while then ask for a retest of B12?



Thyroxine for 32 years, my dose should have been increased by 25mgs a day 3 months ago! I was told at the time that 'you are well within range' but that I had a high LF test and would be sent for a scan................never happened. No mention of blood sugars or anything else. For the following 8 weeks I have felt exhausted, blurry vision, thirsty was told it was stress.......insisted on a blood test. Hey presto........... in three months I have become a type 2 diabetic now on 1500 Metformin and 80 Ziclazide and 200 mgs of thyroxine. Unbelievable, it has been suggested that the shortage of thyroxine has tipped me into diabetes. Apologies from Dr but I now have a lifelong problem - my question - could the lack of thyroxine really has pushed me into diabetes? As I have never seemingly had a problem with blood sugar I thinks its a real possibility.


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