Effects on blood tests of over medication and o... - Thyroid UK

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Effects on blood tests of over medication and or non compliance


Hi I wanted to ask if anyone knows the effects of over medication and or non compliance on blood test results?

With over medication Obviously low TSH but would FT4 and FT3 become below range.?

Would failure to take Levothyroxine correctly (missing doses) cause low TSH with low FT4and FT3?

Kind regards

20 Replies


With over medication Obviously low TSH but would FT4 and FT3 become below range.?

TSH would be low, FT4 would be high mimicking hyperthyroidism.

Would failure to take Levothyroxine correctly (missing doses) cause low TSH with low FT4and FT3?

TSH would be high, FT4 would be low showing hypothyroidism and symptoms would probably reflect that too.

Thank you. The reason I ask is because of a conversation with GP who suggested my results were due to the above and wanted to reduce my thyroxine which is 100mcgs to 75mcgs. I refused and he now says my results are satisfactory with no regard to my hypo symptoms.

Here are the results

8 April 2019

TSH 0.108 Range. (0.38-5.33)

FT4 6.7. (7-16)

FT3 3.8 (3.8- 6)

After discussion another blood test done 24 April 2019 deemed to be satisfactory

Same ranges apply

TSH 0.261

FT4 8.9

FT3 4.5

I think my levels are low but for years now I seem to have a suppressed TSH.

Any advice i supplement with sublingual B12 and take vitamin D, C and selenium.

You have to be more proactive these days I believe.

I always have a low resting heart rate around 55

SlowDragonAdministrator in reply to Blondiejayjay

When were vitamin levels last tested?

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if you have autoimmune thyroid disease (Hashimoto's) diagnosed by raised Thyroid antibodies

Ask GP to test vitamin levels

You may need to get full Thyroid testing privately as NHS refuses to test TG antibodies if TPO antibodies are negative

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Is this how you do your tests

Private tests are available. Thousands on here forced to do this as NHS often refuses to test FT3 or antibodies


For thyroid including antibodies and vitamins

Medichecks Thyroid plus ultra vitamin or Blue Horizon Thyroid plus eleven are the most popular choice. DIY finger prick test or option to pay extra for private blood draw. Both companies often have special offers, Medichecks usually have offers on Thursdays, Blue Horizon its more random

If you can get GP to test vitamins and antibodies then cheapest option for just TSH, FT4 and FT3 £29 (via NHS private service )


Suggest you get FULL Thyroid and vitamin testing privately

Make sure all FOUR Vitamins are optimal

and then get referral to recommended thyroid specialist endocrinologist for correct treatment

Email Dionne at Thyroid UK for list of recommend thyroid specialists


Your results clearly show you need dose increase in levothyroxine

dear Slow Dragon

I have TPO antibodies and Thyroglobulin and diagnosed with Hashimotos. The level of antibodies has been tested twice in 30 years and remained the same TPO 198 and Thyroglobulin 498 (no idea what ranges were).

B12 when last tested was 230 (I supplement because it was 130 but go would not treat due to negative intrinsic factor)

Vitamin D was 68 and I am permanently on prescription of 800 per day

SlowDragonAdministrator in reply to Blondiejayjay

Then your TSH is low BECAUSE of hashimoto’s and LOW vitamin levels

With hashimoto’s we almost always need higher dose vitamin D supplement

Your vitamin D is still too low

improving to around 80nmol or 100nmol may be better



Once you Improve level, very likely you will need on going maintenance dose to keep it there. Often at least 2000iu

Test twice yearly via vitamindtest.org.uk

Vitamin D mouth spray by Better You is very effective as it avoids poor gut function

It’s trial and error what dose we need, with hashimoto’s we frequently need higher dose than average

Local CCG guidelines


Government recommends everyone supplement October to April


do you supplement Magnesium?





Bone pain


Vitamin K2 mk7



If vitamin D is low, B vitamins may be too. As explained by Dr Gominack



B12 also far too low

Supplementing a good quality daily vitamin B complex, one with folate in not folic acid may be beneficial. This also contains B12 and will help improve B12 further


B vitamins best taken in the morning after breakfast

Igennus Super B complex are nice small tablets. Often only need one tablet per day, not two. Certainly only start with one tablet per day after breakfast. Retesting levels in 6-8 weeks

Or Thorne Basic B or jarrow B-right are other options that contain folate, but both are large capsules

If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 7 days before any blood tests, as biotin can falsely affect test results



Low B12 symptoms


What about Ferritin. This needs testing

As you have hashimoto’s are you on strictly gluten free diet? Or tried it?

Hashimoto's frequently affects the gut and leads to low stomach acid and then low vitamin levels

Low vitamin levels affect Thyroid hormone

Poor gut function can lead leaky gut (literally holes in gut wall) this can cause food intolerances. Most common by far is gluten. Dairy is second most common.

According to Izabella Wentz the Thyroid Pharmacist approx 5% with Hashimoto's are coeliac, but over 80% find gluten free diet helps, sometimes significantly. Either due to direct gluten intolerance (no test available) or due to leaky gut and gluten causing molecular mimicry (see Amy Myers link)

Changing to a strictly gluten free diet may help reduce symptoms, help gut heal and slowly lower TPO antibodies

While still eating high gluten diet ask GP for coeliac blood test first or buy test online for under £20, just to rule it out first

Assuming test is negative you can immediately go on strictly gluten free diet

(If test is positive you will need to remain on high gluten diet until endoscopy, maximum 6 weeks wait officially)

Trying gluten free diet for 3-6 months. If no noticeable improvement then reintroduce gluten and see if symptoms get worse






SeasideSusieAdministrator in reply to Blondiejayjay

I agree with Humanbean that I was thinking Central Hypothyroidism. I was going to ask if you have the results of your thyroid tests when first diagnosed.

It would seem that for some reason the feedback loop is broken and your TSH is not reflecting your low FT4, so this could be Central Hypothyroidism, in which case your GP shouldn't be dosing by TSH but should be basing your dose of Levo on your FT4.

As you are taking sublingual B12, are you also taking a B Complex to balance all of the B vitamins?


I have no idea what my blood test results were when first diagnosed as it was in 1980’s and then again in 1993 when I was started on 25mcg of thyroxine which wasn’t increased until 2001 I think

I’m not taking b complex because my folate was very high over range

SlowDragonAdministrator in reply to Blondiejayjay

Were you on folic acid supplements?

Have you retested folate since starting on B12

Hi no I wasn’t on any supplements at the time and last years test was over for folate and about 230 b12 range used here is 170-900.

SlowDragonAdministrator in reply to Blondiejayjay

Folate likely to have dropped considerably once you started supplementing B12

Suggest you get folate retested

I've looked back at some of your historical posts. It seems to be clear that your doctors are ignoring the fact that you almost certainly have secondary hypothyroidism. In a post from three years ago you mentioned being referred to an endocrinologist. Did this ever happen? And were you diagnosed with secondary or central hypothyroidism? Unfortunately endocrinologists are just as likely to be incompetent about the thyroid as GPs, as far as I can tell from posts on this forum.

Someone with secondary hypothyroidism could well have a healthy thyroid gland. But for it to work as it should your body needs to produce sufficient TSH. Your TSH is always low suggesting that your pituitary is unable to produce sufficient TSH for your needs, perhaps because of disease or trauma.

What is the highest your TSH has been in the last three years? Your doctors appear to be completely incompetent in terms of thyroid treatment.

In your shoes I would self-treat. I would have no patience with doctors leaving me ill and under-medicated for at least three years. (I don't know when your problems started.)

I did see Endo who said that the ‘thyroid antibodies interfere with the assay in someone like me who has chronic autoimmune thyroid’

He suggested and write to Gp to advise a dose of 1.6 mags per kg of weight = 100 and that the aim is to get me mid or higher in the FT4 range.

Other than a full thyroid panel he did no other tests and discharged me to GP.

I always refer GP back to that letter whenever they try to reduce me.

It’s interesting what you say about pituitary gland as I had a lower jaw that grew bigger that upper and had to have bimaxillary surgery this wasn’t evident in my 20s but appeared to develop along with my thyroid disease.

But you know these doctors don’t look holistically and don’t like you to suggest things either

Does referring GPs back to that letter actually help? Because from what I've read in some of your other posts they are constantly trying to reduce your dose based on the TSH - they never note down that your treatment should not be determined by your TSH.

I think you would probably do much better to treat yourself. You know how you feel, and that is more important than anything else. You already do medichecks tests for yourself. Perhaps you could take the next step and introduce T3 or try NDT. Then you wouldn't need to involve your doctor in your thyroid treatment at all.

Are you aware that you can refuse to have tests done if you want to? Nobody can force you to be tested or treated if you don't want to. For example, I refuse to have thyroid function testing and cholesterol testing done by my doctors. (I should make it clear that if you want your doctor to treat you then you don't really have any choice over the testing.)

One thing to be aware of though... If you do branch out and start treating yourself your doctor may cancel your right to free prescriptions (which is only of relevance to patients aged 18 or over and under 60 in England).

In reality the letter doesn’t help me achieve optimum treatment but it stops the GP reducing my prescription.

Honestly, they say that my symptoms could be due to over medication.

I’m terrified of a dose reduction because in 2014 I was asked to reduce from 75 to 50 I dutifully did do and ended up in hospital with chest pains and high blood pressure. I had high cholesterol and ‘plaque’ in my heart which was dealt with via angiogram. My pulse was just 40.

A junior doctor writes to my GP stating I am hyperthyroid!

So I think this is where the GP keeps thinking the TSH indicates that I need a reduction.

Honestly, they say that my symptoms could be due to over medication.

Doctors don't know what the symptoms of thyroid disease are, in many cases. There are some symptoms that can occur in both hypothyroidism and hyperthyroidism.

However I've never heard of someone having a pulse rate of 40 while being hyperthyroid. That should have been a whopping clue to your doctors you were under-treated.

Low T3 is known to be very bad for the heart. But of course, doctors avoid questioning on that a lot of the time because they so rarely test it.

If you have low in range or under the range Free T4 then how can you be suffering from over-medication? My guess would be that the doctors would come out with some crap like "if your body wanted more thyroid hormone it would produce more TSH, so your low levels are obviously normal for you". I've had something like that said to me, although my TSH does at least get over the reference range - just.

One thing you could do with your results is to tabulate them and instead of using numbers within a reference range you could convert them to percentages through the range.

For example :

1) Free T4 of 8.9 with a ref range of 7 - 16 is 21% of the way through the range.

2) Free T4 of 6.7 with a ref range of 7 - 16 is 3.3% of the way under the range (or -3.3%, whichever way of describing it you prefer).

For calculating the percentage through the range for any test with a ref range this link is helpful.


It mentions Free T3 and Free T4 but you can use it for anything with a range with a lower limit and an upper limit, and it copes with values under and over the range.

Thank you for this that’s a really good idea.

I will do that

SlowDragonAdministrator in reply to Blondiejayjay

Any head/neck/jaw surgery could obviously have affected thyroid

If you are prescribed 1.6mcg per kilo would this give you a dose increase?

No I’m 60 kg so that would be 96mcgs

SlowDragonAdministrator in reply to Blondiejayjay

Lactose intolerance is common with hashimoto’s.

Lactose intolerance frequently increases dose of levothyroxine needed


Lactose intolerance was diagnosed in 75.9 % of the patients with HT


These findings show that lactose intolerance significantly increased the need for oral T4 in hypothyroid patients.

Wow! I didn’t know about lactose intolerance . Time for some dietary changes


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