Does FT3 and FT4 rise or fall later in the day ?

[lucylocks]

Hi

the reason I ask the above questions is, last week I went for my annual blood pressure check. I had an early evening appointment, they told me I may need some blood tests at the same time. Thinking they may check my thyroid (I know this should be a morning test) but I thought they would only test TSH which is always suppressed, so I agreed to the early evening appointment.

I have just got my results and I am very surprise to see they have tested my FT3 and FT4

Results

TSH <0.02 range 0.35 - 4.70

FT4 12 range 7.80 - 21.00

FT3 4.2 range 3.80 - 6.00

I did not take my 125mcg. levo. in the morning of test, nor did I fast.

So how do my results look considering the time of day they were done.

Any advice would be gratefully received.

Thank you.

[SeasideSusie Remembering]

lucylocks

The first post in this thread shows the daily rhythms of TSH, FT4 and FT3, so you can see how they vary during 24 hours and the difference it would have made to your results:

healthunlocked.com/thyroidu...

Fasting would only possibly affect TSH. Assuming "early evening" means around 6pm, TSH is going to be much lower than if done at a 9am blood draw but if your TSH is usually suppressed it probably wouldn't make much difference anyway.

[lucylocks in reply to SeasideSusie]

Many thanks for your reply, and the link.

So from the graph, all levels are lower in the evening

Bloods were taken at 7.00 pm. Looking at the graph I have worked out that if I had had bloods taken at 9.00am my results would be,

TSH 0.47 so just above bottom of range.

FT4 12.75

FT3 4.6

So FT4 and FT3 still low, so would an increase in levo be advisable ?

I would add though that when last tested my B12 folate and Vit D were pretty low in range, would this have a bearing on my thyroid results ?

[SeasideSusie Remembering in reply to lucylocks]

I don't know how you can accurately work out what your results would be if you'd had your test at 9am so I wouldn't rely on your guesstimate.

I wouldn't suggest any change in your dose until I'd seen a set of results done under the conditions always advised here:

* blood draw no later than 9am

* fast overnight from evening meal/supper the night before

* water only to drink before the test

* last dose of Levo 24 hours before blood draw

Nutrient levels need to be optimal for thyroid hormone to work properly :

Vit D - 100-150nmol

B12 - top of range for Total B12, at least 70 (preferably over 100) for Active B12

Folate - at least half way through range

Ferritin - half way through range

[lucylocks in reply to SeasideSusie]

Thank you,

I doubt very much that the surgery will re do the test so, I will get the Medichecks Thyroid/Ultra Vit test to check everything.

If my nutrient levels improve, and these improve thyroid hormones to work better, then an increase in levo. may not be needed ?

[SlowDragon Administrator in reply to lucylocks]

Improving vitamin levels helps thyroid hormones

This often enable you to get dose of levothyroxine increased

Come back with new post once you get Medichecks result

As you know your vitamin levels are low are you taking supplements?

If taking any supplements that contain biotin remember to stop taking a week before any blood tests as biotin can falsely affect test results

[lucylocks in reply to SlowDragon]

Thank you.

[Hay2016 in reply to lucylocks]

Did you factor in how long since your last dose too? If you take it in the morning it’s nearly 36 hrs since last dose. Over the 24hrs recommended. Xx

[lucylocks in reply to Hay2016]

Thank you,

so leaving 36 hours would have made my levels lower ?

[Hay2016 in reply to lucylocks]

Yes. With all the different variables unfortunately your best guess is probably very off. Xx

[lucylocks in reply to Hay2016]

Thank you I shall get them done again privately.

[Wildbird]

I think that they have tested your free t4 and t3 because your TSH reading is so low. They would have been looking to see if you were over replaced. Those results show no such thing and prove that their reliance on TSH as a marker of thyroid health is misplaced. Your free t4 seems low, as does the free t3.

[lucylocks in reply to Wildbird]

Many thanks for your reply.

It is interesting you say they tested my FT3 and FT4 as my TSH is so low, on other occasions they have not bothered.

Hopefully they may start to realize, as you say, the TSH marker is misplaced.

Please see my reply to SS above, I would think I need an increase in levo.

[Eliotf]

Lucylocks- my understanding is generally the taking of the pill(s) affects the reading & if you are eating while taking the pill. The half life of t4 is about 7-10 days. The t3 half life is about 6 hours. Exercising on a regular basis does make your body more efficient so then you would need less. Just not from one day to the next day. I had that issue of exercise issue. Generally speaking the difference between morning & night is due to if you take the pill before or after the test

[lucylocks]

Thank you.

[momindenver]

By any chance were you taking biotin? This can affect the results.

[lucylocks in reply to momindenver]

Hi

No I was not taking biotin, thank you for your reply.