Blood Test Prep

[wallofbeans]

Hi All,

I'm due another blood test for my under active thyroid, and wondered if I should stop taking my medication before I have it.. or am I better off continuing to take it as normal? What's the best way to get an accurate result?

Thanks!

[SeasideSusie Remembering]

wallofbeans

No, you don't stop taking your medication, but there are recommended times between last dose of thyroid meds and blood draw.

If taking Levo, leave 24 hours between last dose and blood draw.

If taking T3 - in addition to Levo, on it's own, or NDT - leave 12 hours between last dose and blood draw.

[wallofbeans in reply to SeasideSusie]

I am taking Levothyroxine. I haven't had it for two days now and was going to get my blood test today. Is that too much? It's a drop in centre for blood tests so can change when I do it if needed.

[SeasideSusie Remembering in reply to wallofbeans]

wallofbeans

Yes it is too much. It will give you a false low FT4.

Thyroid blood tests should be done at the first appointment of the morning, no later than 9am, leaving breakfast until after the blood draw and only drinking water. This is because eating and coffee, in particular, can affect TSH. TSH is highest early hours of the morning and lowers throughout the day, so as most doctors dose by TSH then to avoid a reduction in dose of Levo, or when looking for an increase, it's best to have TSH as high as possible. And to get the normal level of circulating thyroid hormone (FT4) then last dose of Levo should be no more than 24 hours before blood draw. Also, taking Levo before a blood draw gives a false high FT4.

[wallofbeans in reply to SeasideSusie]

Ok. Thanks. I've now taken meds for today and will go tomorrow.

[SeasideSusie Remembering in reply to wallofbeans]

wallofbeans

But if you've missed 2 days of Levo, you wont have been taking your normal dose . Personally, I would continue my normal dose for the rest of this week to get back on track then aim to have a blood draw early next Monday morning no more than 24 hours after last dose of Levo.

[wallofbeans in reply to SeasideSusie]

I need to get it done ASAP. The docs have given me limited meds as this is my annual review and I'm going on holiday in two weeks and need to have it sorted by then.

[SeasideSusie Remembering in reply to wallofbeans]

wallofbeans

If FT4 is not important with this test then you will be fine. If your GP is dosing by TSH then bear in mind that it's highest early in the morning, before food and water only if you want to avoid a reduction in dose or looking for an increase.

[wallofbeans in reply to SeasideSusie]

Sorry, I don't know what "FT4" means and so don't know if it's important. I'm also not sure what "dosing by TSH" means either..?

[SeasideSusie Remembering in reply to wallofbeans]

wallofbeans

FT4 is the Free T4 test which tests the amount of thyroid hormone (T4) that is circulating in our blood. To feel well most hypo patients need FT4 in the upper part of the range.

Dosing by TSH means your doctor using the TSH test result to adjust your dose of Levo. Dosing by TSH is wrong, TSH is not a thyroid hormone, it is a signal from the pituitary gland. When you have enough thyroid hormone the pituitary gland detects this and TSH will be low, if you don't have enough thyroid hormone the TSH will be high. So if a doctor sees a very low TSH they tend to think we are overmedicated - this is not the case, it just means that the pituitary gland detects the thyroid hormone we are taking and whether or not we are taking enough. It's actually the Free T3 (FT3) test which tells us if we are overmedicated or not, unfortunately doctors have had an information bypass where this is concerned and this is why so many hypo patients remain unwell.

It would be a good idea to get into the habit of always asking for a print out of your test results (not verbal or hand written results) and follow your progress. Make a note - diary or spreadsheet - indicating date of test; test result; reference range; dose of Levo; how you feel, etc. This way if your GP wants to adjust your dose and you know you wont feel well on that dose, you can refer to your previous results to discuss how you were on that dose. You can always put your results on the forum for members to comment.

[wallofbeans in reply to SeasideSusie]

So should I be asking for the T3 test too?

[SeasideSusie Remembering in reply to wallofbeans]

wallofbeans

You can ask for it but it's not always done. My surgery's lab does it when TSH is suppressed. It's the lab that decides if it's done even when a doctor requests it.

It's Free T3 test (there is another T3 test so best to say Free T3 so there's no mix up).

[Raventhorpe]

Hi Wallofbeans just to mention if your taking any B complex vitamins to stop them for 3/4 days before test as the biotin in them can affect the t4 results.

[wallofbeans in reply to Raventhorpe]

Thanks! Good to know!

[JOLLYDOLLY]

Hi, Yes definitely do not take any thyroid meds before a test as it can give a false reading. Just take them straight after, it won't being late that day.

Hope all goes well.

Take care

[wallofbeans]

The form I have from the doctor says "TSH" and then "Blood (Gold Top) - Chem" and under 'Clinical Details' they have also added "On thyroxine". I'm currently on 125mg of Levothyroxine and have been for a number of years now.

[Heloise]

Levo is synthetic T4 and TSH dosing means that he uses the TSH to determine your dose. The problem is that often your TSH result is almost always lowered because taking Levo causes the adjustment. The FT4 result is a better indicator and if it is in the upper part of the range may mean you are taking enough. But still, that T4 has to convert to FT3 which is the active form of the thyroid hormone and the part that may enter cells and improve health. For some people that conversion isn't taking place as well as it should.

stopthethyroidmadness.com/l...