Thyroid UK
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Can you help me re blood tests

Hi this is only my second post. I need some advice. I am taking 100mcg levothyroxine after TT in June 2016. Originally took thyroxine in a morning, not well tolerated so after reading on this site about taking at night this is what I seems to be much better for me...I started on 100mcg in June but have reduced and increased dose since and am now back to 100mcg. I 'feel' better in myself, still feel tired at times, but not so good on the aches and pains in my knees and now hip and lower back.....I have suffered with osteoarthritis for a number of years, but never in my hip or lower back...I read that sometimes thyroid problems can cause 'aches and pains' in joints, is this correct? My GP is sending me for a blood test and I note she is asking for TSH, T4, T3, vitamin D, B12+Folate, Ferritin....U &E, LFT, Calcium, HbA1c, TFT, Full Blood count, ESR, Rheumatoid Factor....looks like she is covering all.......

Could someone tell me if I need to fast before test and do I take my Levo the night before or do I not? No one has suggested this to me before blood test that I have previously had....

I have also, in the last few months started having problems with my eyes....ophthalmologist seem to think it is TED.....I am having an MRI on my orbits next week. What will happen next, I thought all my problems would disappear after my thyroidectomy, but it seems not......any suggestions how I can help myself to feel 'well' again would be much appreciated....

Oh, by the way I am nearly 65 years old and overweight!

This is all very new to me and any advice would be much appreciated.....

8 Replies

Yes, you do need to fast (you can drink water) and you also have to leave approx 24 hours gap between last dose of levo and the test and take afterwards. This allows the TSH to be at its highest as it drops throughout the day and makes the difference in getting hormones adjusted unnecessarily.

I had widespread pain and stiffness when on levothyroxine.

As you have had a TT I'd also ask for a Free T4 and Free T3 - these are very important, particularly with a TT. You need to know exactly how much T3 is circulating in your blood as it is T3 which is the active hormone (T4 is inactive and has to convert to T3 and sometimes doesn't do so efficiently).

My personal opinion and I'm not medically qualified is that anyone whose had a TT should have liothyronine (T3) added to T4.

Also recent research has shown that all hypothyroid patients feel better when T3 is added to T4. One of our Advisers Research Team had their paper accepted.


If you had TT done due to Graves you might benefit from trying gluten free diet

1 like


Your GP has ordered all the tests we recommend on the forum plus some additional ones.

Make sure you take your Levothyroxine at least 8 hours before your blood test. The blood test should be early in the morning when TSH is highest and you should fast overnight as TSH drops after eating and drinking. Drink plenty of water before the blood draw to avoid dehydration.

Graves doesn't disappear after thyroidectomy and the antibodies may go on to attack other organs, particularly the eyes, causing thyroid eye disease (TED).

If you are under medicated on 100mcg that will cause a flare up in TED and joint and muscle pain. Ideally TSH will be suppressed <0.1 to reduce TED flares.

Low ferritin, vitamin D, B12 and folate may also cause musculoskeletal pain.

Ask for a printout of your results and ranges and post them in a new question and members will advise.


Thank you. I will omit my Levo the night before my test and just drink water. You say to take afterwards, as this will mean taking one after test in the morning, is it still ok to take my normal one that night? This will mean 200mcg in the space of 12 hours, is this ok?


I am a bit confused...'shaws' says to leave 24 hours from taking Levo to test...'clutter' says to take Levo 8 hours before test! Please I take my Levo the night before as this will be 8 hours before test...or do I not take it to allow the 24 hour before test?.


Foxie, there is no hard and fast rule about this. The two important apsects are: A minimum of 8 hours and no more than 24 hours between taking medication and getting blood drawn. Consistency - whatever you do this time, do the same next time and the time after etc.


Hi Foxie1234, I believe 24 hours gap is recommended as this is supposed to raise your tsh and lower ft4, reflecting the typical level without the levo dose in the blood. Just be mindful that this won't work if this gap is substantially more than 24 hours (as you take yours in the evening then test in the morning it would apply). I discovered this after my last bloods and the gap was c. 29 hours. This longer gap meant that my ft4 level was lower and perhaps the tsh higher than I intended (have a look at my recent post) .


On the day before your test take your Levo 24 hours before your blood test appointment. So if your blood test is at 8.30am on Tuesday, then take your Levo on the Monday at 8.30am. Don't take any Levo on Monday night.

Your blood test appointment needs to be as early as possible, before 9am if you can possibly wangle it.

Assuming that you have managed to book an early blood test, don't eat or drink (except for water) for about 8 - 10 hours before the test.

On the day of the test take your Levo in the evening as usual.

If you haven't managed to get an early appointment, then don't fast. It wouldn't be healthy, and I don't know what the effect of prolonged fasting is on thyroid function test results.

The reasons for the above recommendations is :

1) Avoiding Levo for 24 hours reduces the risk that your Free T4 will be over the range. If your result was very high in range or over the range you might get meds reduced and most people don't want that.

2) Avoiding Levo for 24 hours, and using the same gap every time you have a test, means that you can compare tests more reliably.

3) Having your test as early as possible in the day will give you the highest possible TSH. Since TSH is what most doctors use as their guide to treating patients you want yours to be as high as possible to reduce the risk of getting your meds reduced. TSH has a circadian rhythm. See the first set of graphs on this research paper :

Highest TSH shows up in the TSH graph in the middle of the night. Lowest TSH shows up in the afternoon. Since blood tests aren't done in the middle of the night, the best we can get is a test done as early as possible.


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