Thyroid UK
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I am being referred for a fasting glucose test and a liver function test. Can anyone give their thoughts on this please?

My Levo was reduced from 150 to 125 about two months ago, even though I still had symptoms. The TSH and T4 test showed that I was now hyper. When I was retested I was told that the levels were better but I should remain on the lower dose for a further six weeks and then have a further test. At the GP appt I asked for B12, Vit D and ferratin. I phoned up this morning to see if the results were back and am now being sent for the further tests above. I was advised to do this as soon as possible and am now really worried that I may have diabetes, although I have no symptoms. I have read that sometimes blood sugar levels can be affected by the thyroid but can't really find out much more. Can anybody out there help please???

Many thanks

14 Replies

The only way of telling you have diabetes with a blood test is if you fasted at least 8 hours before blood was drawn.

I've had the glucose tollerance test, it was fine you just hang around for a long time, gathering urine sample,s having your thumb pricked for blood. The glucose drink is pretty disgusting because it is soooo sweet. All in all nothing to worry about.

I think any of these tests should be repeated before a diagnosis of diabetes being made.


Thanks - I think that's why I have to do the fasting one tomorrow. What's the glucose tolerance test for (other than the obvious!!!!)?


The glucose tollerance test actually measures your body's reaction to glucose and how quickly the glucose goes up in your blood. It's also a measure to see if the kidneys are letting the glucose get into your urine.

The blood one measures average blood glucose levels over the previous 3 months. It is really important to follow the fasting advice, because even a cup of tea with milk will mess it up. You can drink water but nothing else, and don't cheat and have a piece of toast at midnight lol!


How did you know I might be tempted???

Thanks very much


Lol! X


Do you have your test results? Especially the ones which seemed to indicate you being hyper.

Did you take levothyroxine in the, say, 12 hours before the blood was drawn? What time of day did you have the blood drawn?



Thanks Rod

I have results for 3 dates

30.5.12 - I was taling 150 Levo at this point

TSH 3.207 (Range 0.3 - 5.0)

Free T4 19.1 (Range 9 - 24)

12/3/13 - my dosage was reduced to 125 based on this

TSH 0.137 (0.3 - 5.0)

Free T4 25.3 (11 - 23)

2/5/13 after c6 weeks on 125 Levo. I didn't take my dose before this test but always have done in the past.

TSH 0.09 (0.3 -5.0)

Free T4 23.2 (11 -23)

My other test results are

Blood glucose 8.9 (3.6 - 7.8) - classed as high + sent for fasting glucose and HbA1c

B12 - 410 (172 - 11) - classed as normal

Folate - 17.2 (4.6 - 18.7) - again normal

Ferritin - 137 (12 - 323) - again normal

Sodium - 139 (133-146) - normal

Potassium - 3.3 (3.5 - 5.2) - low - to be retested in 1 month

Urea - 7.2 (3.0 - 8.5) normal

Creatinine 73 (0-115) Normal

GFR MDRD - 71/73m2

I suppose I am worried about the potential diabetes but will find out soon enough.




Nothing looks terrible to my eyes! The thyroid levels seem quite sensible.

Not in the least surprised you are concerned about diabetes - anyone would be. I don't know much about diabetes - on its own or with thyroid disorder.

Have a look at 9.5.1 here:

Not easy reading but might help.



Thanks - it seems there may be a link between hypothyroid and insulin resistance but I'm not sure which is the chicken and which is the egg! I think I'll look at more info on diabetes and keep my fingers crossed.

Thanks again



I rather duck out of that question as well! (Seeing as we are talking chickens and things...)

Hope it goes well.



New paper (abstract on PubMed):

J Diabetes Res. 2013;2013:390534. doi: 10.1155/2013/390534. Epub 2013 Apr 4.

The Relationship between Type 2 Diabetes Mellitus and Related Thyroid Diseases.

Wang C.


Department of Endocrinology, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, 2800 Gongwei Road, Huinan Town, Pudong, Shanghai 201399, China.


Type 2 diabetes mellitus (T2DM) has an intersecting underlying pathology with thyroid dysfunction. The literature is punctuated with evidence indicating a contribution of abnormalities of thyroid hormones to type 2 DM. The most probable mechanism leading to T2DM in thyroid dysfunction could be attributed to perturbed genetic expression of a constellation of genes along with physiological aberrations leading to impaired glucose utilization and disposal in muscles, overproduction of hepatic glucose output, and enhanced absorption of splanchnic glucose. These factors contribute to insulin resistance. Insulin resistance is also associated with thyroid dysfunction. Hyper- and hypothyroidism have been associated with insulin resistance which has been reported to be the major cause of impaired glucose metabolism in T2DM. The state-of-art evidence suggests a pivotal role of insulin resistance in underlining the relation between T2DM and thyroid dysfunction. A plethora of preclinical, molecular, and clinical studies have evidenced an undeniable role of thyroid malfunctioning as a comorbid disorder of T2DM. It has been investigated that specifically designed thyroid hormone analogues can be looked upon as the potential therapeutic strategies to alleviate diabetes, obesity, and atherosclerosis. These molecules are in final stages of preclinical and clinical evaluation and may pave the way to unveil a distinct class of drugs to treat metabolic disorders.





Thanks Rod - this looks really helpful. If I am diagnosed I will certainly share it with whoever treats me.



Just wanted to say thanks for your advice and info. Fasting glucose blood test results came back today - Normal!!!!. Although we are often suspicious of "normal" test results I think I'll take this one at face value.

Thanks again



Don't blame you - so would I.


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