blood sugars raised!: Ive been on Levothyroxine... - Thyroid UK

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blood sugars raised!

Chicadee16 profile image
28 Replies

Ive been on Levothyroxine for two years and after my blood sugars (always low previously) are pre diabetic. Ive read that Levo can do question is: what can I do about it? Will changing the brand of Levo help?

Also Ive read that if you've been on Levo for two years, its hard to come off it as the Thyroid relies on it. Does anyone know if this is true?

28 Replies
Lalatoot profile image

Chicadee It is not the levo that is the problem, it is caused by being hypo and having low thyroid hormone levels. Thyroid dysfunction can affect a person's insulin and blood sugar levels, which can contribute to the development of diabetes.

If you are hypo you need to take thyroid hormones to replace what your body would have produced. The most common and widely available replacement hormone is levo. The alternatives are ndt and liothyronine which are not readily available on the nhs and which you would need to read up about before you think about going down that route.

Chicadee16 profile image
Chicadee16 in reply to Lalatoot

hello and thanks for the reply. When you say "Thyroid dysfunction can affect a person's insulin and blood sugar levels, which can contribute to the development of diabetes." I can understand that happening when you are NOT on the medication but why and how does the medication increase your blood sugars and what can be done about it....that is my query...

Lalatoot profile image
Lalatoot in reply to Chicadee16

It is being on the wrong dose of medication that is the problem. Levo thyroxine replaces the hormones your thyroid would have made. An average normal person has a TSH usually around one and an ft4 roughly 50% through range and the body adapting the hormone levels according to our needs.

For a person with thyroid problems this system of levels and feedback loops is disrupted and broken. If we do not take enough T4 or, for those who need a combo, enough T4 and T3, we still have symptoms. And because we are reliant on a daily oral dose or doses of hormones and our body cannot automatically produce more if we have a period of increased activity or stress for example, our hormone levels may have to be higher to compensate for this.

Also our conversion from T4 to T3 can be less efficient so our Ft4 level may need to be slightly higher than it would have been normally again to compensate for this.

The bottom line is, even though you are on levothyroxine you can still have too low levels of thyroid hormones (which equates to the thyroid disfunction in normal folks). It is being on too low or too high a dose of levo that is the problem . The dose of levo has to be optimal for you.

What can be done? You need to monitor your blood results and vitamin levels to try to get on the best dose of levo for you and to ensure that your body can use the levo efficiently.

How do I do this? If you post thyroid blood results and vitamin levels on here then folks will comment from their experiences and help to see if you can fine tune your dosage for your needs and reduce symptoms.

greygoose profile image

Also Ive read that if you've been on Levo for two years, its hard to come off it as the Thyroid relies on it.

Why would you want to come off it if you are hypo? Unless you're changing to T3 only or NDT. You cannot live without thyroid hormone. But coming off levo to take something else wouldn't be a problem at all.

But, taking levo (T4) has nothing to do with the thyroid itself. The thyroid doesn't 'rely' on it. But, all the rest of your body does. It doesn't affect the thyroid directly at all. But, taking thyroid hormone replacement - levo, etc. - does reduce your TSH, so that it no-longer stimulates the thyroid to make thyroid hormone so it goes to sleep, as it were. Stop the levo and the TSH will rise and stimulate the thyroid to make as much hormone as it is capable of making - which obviously isn't enough to make you well or you wouldn't be on levo in the first place. :)

Chicadee16 profile image
Chicadee16 in reply to greygoose

hi Greygoose. Thanks for your reply. I dont want to come off of levo, it was something I read on an American medical website. I will ask my GP about this...

greygoose profile image
greygoose in reply to Chicadee16

And do you really think your GP will know? Obviously the 'medical' that wrote this nonsense didn't know the first thing about thyroid! :)

SlowDragon profile image

a few questions

How much levothyroxine are you currently taking

Do you always get same brand levothyroxine at each prescription

ALWAYS test thyroid levels early morning, ideally just before 9am and last dose levothyroxine 24 hours before test

Please add most recent thyroid and vitamin results and ranges

What vitamin supplements are you currently taking

Do you have autoimmune thyroid disease, also called Hashimoto’s, usually diagnosed by high thyroid antibodies

Approx how much do you weigh in kilo

Private tests are available as NHS currently rarely tests Ft3 or all relevant vitamins

List of private testing options and money off codes

Medichecks Thyroid plus antibodies and vitamins

Blue Horizon Thyroid Premium Gold includes antibodies, cortisol and vitamins

Chicadee16 profile image
Chicadee16 in reply to SlowDragon

hello SlowDragon I have done all the private blood tests. My issue isnt my results, its WHY and IF the levo raises blood sugars and what can be done about it.

SlowDragon profile image
SlowDragonAdministrator in reply to Chicadee16

Increased HBa1c suggests you’re not on high enough dose levothyroxine

Which is why I asked what your results are

Chicadee16 profile image
Chicadee16 in reply to SlowDragon

thank you, I will ask my GP about this. The results showed I was adequately medicated, dosage wise.

SlowDragon profile image
SlowDragonAdministrator in reply to Chicadee16

please add results

We see thousands of people on here left on too low a dose of levothyroxine

Just testing TSH is completely inadequate

You need TSH, Ft4 and Ft3 tested early morning, ideally just before 9am and last dose levothyroxine 24 hours before test

Plus all four vitamins at OPTIMAL levels

What vitamin supplements are you currently taking

What were most recent vitamin results

How much levothyroxine are you currently taking

Approx how much do you weigh in kilo

Lovecake profile image
Lovecake in reply to Chicadee16

adequate? For whom? We are all different and your doctor’s “adequate” might not be adequate for you.

SlowDragon profile image

Suggest you reread my replies in these previous posts

in particular this post

shows you had low vitamin D

how much vitamin D have you been taking

Have you retested vitamin D since this ?

Ft4 was 62% through range 

But ft3 only 14.6% through range 

Most people when adequately treated will have Ft3 at least 50% through range

Extremely poor conversion of Ft4 to Ft3

Ft3 is the active hormone and the most important result

Have you had coeliac blood test done

Are you now on strictly gluten free diet or dairy free diet

Likely to need addition of T3 prescribed alongside levothyroxine

Email Thyroid U.K. for list of recommended thyroid specialist endocrinologist and doctors who will prescribe T3

Chicadee16 profile image

the doctor said my ranges were ok. Are you saying they arent?

Doctors words
helvella profile image
helvellaAdministrator in reply to Chicadee16

I often post the text and link below because it is one of the best papers about reference intervals - normal ranges.

Because it comes from the medical world, written by medics and published in the British Medical Journal, it should be convincing to healthcare professionals.

It is also written in a way that is reasonably accessible to many patients, at least with a bit of careful reading.

The normal range: it is not normal and it is not a range


The NHS ’Choose Wisely’ campaign places greater emphasis on the clinician-patient dialogue. Patients are often in receipt of their laboratory data and want to know whether they are normal. But what is meant by normal? Comparator data, to a measured value, are colloquially known as the ’normal range’. It is often assumed that a result outside this limit signals disease and a result within health. However, this range is correctly termed the ’reference interval’. The clinical risk from a measured value is continuous, not binary. The reference interval provides a point of reference against which to interpret an individual’s results—rather than defining normality itself. This article discusses the theory of normality—and describes that it is relative and situational. The concept of normality being not an absolute state influenced the development of the reference interval. We conclude with suggestions to optimise the use and interpretation of the reference interval, thereby facilitating greater patient understanding

►Health is a relative and not an absolute state.

►The reference interval acts as a comparator for the patient’s blood result. It is not the arbiter of whether disease is present or not.

►Natural fluctuations in a blood result can occur.

►Comparison of a result against the reference interval should be informed by the clinical suspicion made beforehand.

Freely accessible here:

humanbean profile image

It's a common misconception that taking Levothyroxine heals the thyroid. It doesn't. What happens is...

1) People with thyroid disease have damaged thyroids. In most people with hypothyroidism the damage is caused by autoimmune disease.

2) Damaged thyroids produce insufficient thyroid hormones for good health.

4) When people take Levo their thyroid (assuming they have one) will reduce its output of T4 and T3.

5) Taking Levo does NOT top up the the output of the thyroid, it replaces it.

6) If someone on Levo stops taking it, given time their thyroid will go back to producing whatever thyroid hormone it is capable of. Any damage it has suffered will still be there and may even be worse than it was. But this situation has nothing to do with taking Levo. It is (usually) a result of autoimmune disease.

Chicadee16 profile image
Chicadee16 in reply to humanbean

many thanks I will have a read!

Chicadee16 profile image
Chicadee16 in reply to humanbean

many thanks. I am aware of the facts that you stated here but I’m sure it will be helpful to others so thank you. . 😁

CoeliacMum1 profile image

So we’re your blood sugars ok before having a thyroid problem, did you have a Hba1c test with thyroid condition but not yet started with thyroid medication to be sure it’s definitely medication?

I can see just by googling that they say thyroxine rises blood sugar although never looked at my leaflet although it’s in leaflet for Liothyronine (T3) also, but also thyroid condition cause onset of all manner of hormone shifts, It’s a hard one to say which caused it however, dietary wise you can help yourself in trying to keep those levels down.

Obviously stay clear of lots of sugary things and fruit juices, starchy carbs need to be watched too, maybe reduce portions.

We need carbs but you can choose better carbs to eat that release slowly and don’t cause spike our blood sugar, there’s a few hacks to keeping blood sugar steady.

Look at Glucose goddess on social media for areas to help keep blood sugar stable, sometimes it’s simply an order of eating a meal.

I’ve found myself with increasing Blood sugar levels 7 yrs ago few years in on thyroid meds, as we age we become less tolerant too though, then add in conditions and medication it’s another battle, but achievable.

Mine was eating all the free from alternatives (as coeliac) as soon as ditched those my levels naturally dropped, so eating non processed foods really helped, mines on higher side of normal and I generally eat what I want just more mindful of what I’m eating now.

Choose brown rice, pasta and if can tolerate it pasta made with higher fibre like chickpea and lentils etc.

Reducing starchy carbs, removing the white bread, rice and pasta can help somewhat it maybe all you need to do, if still too high need to reduce the amount you have then you can fill up on vegetable non starchy carbs, that contain more fibre that offsets the glycemic load.

White potatoes are like sugar bombs to me…I feel hungrier after eating than if never had them … eventually you’ll make connections with what triggers you. If you leave potatoes to go cold after cooking, the resistant starch in them has properties to decrease insulin sensitivity. I have found I can eat these much better and obviously good for your gut microbes.

Chicadee16 profile image
Chicadee16 in reply to CoeliacMum1

many thanks for your help. I didn’t have a pre Levo blood test for glucose but would be surprised if they were up before thyroid issues and before taking levo as I’ve always had low blood sugar and got the shakes if I didn’t eat regularly. I’m doing intermittent fasting and am aware of the foods to eat so will plough on with that and also ask GP. Although as you say it’s hard to know definitively if it’s the drugs.

CoeliacMum1 profile image
CoeliacMum1 in reply to Chicadee16

That’s interesting re shakes, I’ve had that since early teens (4 decades) and always assumed hypoglycaemia but no blood tests to prove it was low on those occasions just these crashes I’d periodically get.

On quizzing my GP she says it’s actually also can be related to out of control blood sugar, although it’s a symptom of lower blood sugar at that point, it’s crashing due to being higher previously and not staying steady, that’s how it was explained to me, and still can be related to high blood sugar levels especially if getting repeated high HbA1c blood test results.

That was my scenario anyhow,

Chicadee16 profile image
Chicadee16 in reply to CoeliacMum1

many thanks for your reply

pacific-paradise profile image

Chicadee, are you taking statins?

Chicadee16 profile image
Chicadee16 in reply to pacific-paradise

no Im not, but my husband is and his blood sugar levels are raised too! Seems to me that these drugs help one thing, and cause another issue!

pacific-paradise profile image

yeah, you would think the doctors will take care of you without harming you, but sadly that is not the case. It is known that statins cause type 2 diabetes and permanente muscle damage and yet doctors prescribe those horrible things to you. 😭

Chicadee16 profile image
Chicadee16 in reply to pacific-paradise

its a real worry thats for sure!

Gilbo72 profile image

Hi Chicadee16 , I started Liothyronine a few months ago, in addition to levothyroxine that I have been on for 10 years.

I was shocked to find my Blood glucose went up quickly. It had always been a bit on the high side after starting Levo/or getting ill, but it definitely increased, and I started having food coma's after eating anything, which I never had before.

It actually states in the Liothyronine paperwork that the medicine can raise your blood glucose levels, but no reason to why. I have spent some time looking into it.

Last month I went to my endo, and found my BP had also increased significantly. Again it was always a bit high, as are my cholesterol levels and my kidney GFR was quite low.

I was under the impression, that correctly medicated, everything 'resolves'. Sadly it is not the case. You are playing with hormones and they all interact in a delicate balancing act.

I came away from my appointment and cried. I have been feeling so much better on the addition of T3 but couldn't believe that from someone who was extremely fit and healthy before Hashimotos, now had all these levels creeping up. My BP was 153/92. I asked the nurse to take it several times! My fasting glucose had risen to 6.8. I was basically looking at a life of prediabetes and a stroke risk.

Anyway, looking into it, it does seem Levo and Lio medication do indeed raise blood glucose by 10-20 points.

However, a recent case study published in March 2015 puts an interesting spin on this topic. The study was entitled “Recurrent hypoglycaemia in type 2 diabetic patient due to hypothyroidism.” The author discussed that a type 2 diabetic patient had trouble with low blood sugar. The low blood sugar was not due to medical over-treatment for diabetes, or other problems with liver or kidney health. The patient was found to have problems with low thyroid function and was subsequently started on levothyroxine. The levothyroxine elevated the patient’s blood sugar to the point where hypoglycaemia resolved and thyroid levels improved.

The medical commentary and interpretation was that the levothyroxine normalized blood sugar because the thyroid was under functioning. On the first read, the levothyroxine seems to be the cure because of faulty thyroid function. However, if you think about this from the context of levothyroxine elevating blood sugar as a side effect, it creates a different spin.

The endo was happy to test my blood levels and get my blood pressure monitored, but that was all. I realised I was on my own and spent some time looking at lifestyle changes. I have always believed I ate healthy and I know I am now quite sedentary. There were two schools of thought about diet for blood sugar. Ketogenic (low carb, high good fats) , but then I came across Whole-food, plant based diet. ( High carb, vegan, low fat). I looked into both, watched loads of TED talks, podcasts and YouTube and found the science behind the latter enlightening, with additional benefits of reversing heart disease and lowering BP and so have been eating like that for a month. My fasting glucose has already changed to 5.2/ 5.4, and my BP is regularly in low 120's/70 and on happily quite a few occasions, in the 110's/70. (A couple of spikes of 130/late 70's) and the food comas have disappeared. The diet is not for everyone, but I find it is actually easy, satisfying and suits me, and I have a feeling I may now stick to it forever. (Although I still do walk around laughing at myself, thinking I am very much like Neil out of the young ones!)

Chicadee16 profile image
Chicadee16 in reply to Gilbo72

hello Gilbo thanks very much for your reply. Do tell me more about the diet you are on....can you send some links?

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