Thyroid function test results

[Wilko91]

I have been on Levothyroxine for 10 years. My dose increased from 100mg to 125mg in Nov 2011. Has a test last week and this time they included T4 ( missed on a few occasions) my result TSH= 1.21 T4= 23.4. Im a bit confused yes T4 is raised, but isnt it still within normal ranges? Got a phone consultation with GP next week. Im not good a regular taking ( time wise) of thyroxine. I had it late in the day, the day before the test, and about an hour before on the day. Could that give an elevated T4 reading in anyones experience? Many Thanks John

[SeasideSusie Remembering]

Wilko91

my result TSH= 1.21 T4= 23.4. Im a bit confused yes T4 is raised, but isnt it still within normal ranges?

We can't say whether it's within the normal range because you haven't given us the range. Reference ranges vary from lab to lab, they're not universal, so we need the range that came with your result. But from all the different ranges we see here, I'd say it's either at the very top of the range or over range.

Im not good a regular taking ( time wise) of thyroxine.

I'm afraid you are going to have to get into a routine. Decide what time of day you want to take your tablet - be it early morning or bedtime, or whatever suits you, and stick roughly to that time, not to the minute but within an hour or two I'd say. This will then remind you to take your tablet regularly. I take mine in the early hours of the morning when I need a regular bathroom trip, so that's usually around 4-7am.

We always advise to take your Levo on an empty stomach, one hour before or two hours after food, with a glass of water only, no tea, coffee, milk, etc, and water only for an hour either side, as absorption will be affected. Take any other medication and supplements 2 hours away from Levo, some need 4 hours.

Taken from GP Notebook gpnotebook.com/simplepage.c...

* when T4 is taken orally, up to 80% of it is absorbed, and the peak serum concentration is reached two to four hours after ingestion

* serum concentration then rises by 20% to 40%

* a fatty meal lowers its absorption by 40% , and even drinking coffee lowers its absorption by 27% to 36%

* consequently, thyroid hormone must be taken in the fasting state, with water, 30 to 60 minutes before breakfast (although we advise as above, one before food or two hours after).

I had it late in the day, the day before the test, and about an hour before on the day. Could that give an elevated T4 reading in anyones experience?

Most certainly taking your Levo an hour before the test will have elevated your FT4 result. You took two doses in probably 12 hours before the test. The test will have measured the dose of Levo you'd recently taken, not the normal circulating amount of T4.

Always advised here, when having thyroid tests:

* Blood draw no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If looking for a diagnosis of hypothyroidism, an increase in dose of Levo or to avoid a reduction then we need the highest possible TSH

* Nothing to eat or drink except water before the blood draw. This is because eating can lower TSH and coffee can affect TSH.

* Last dose of Levo 24 hours before the test, take that day's dose after the blood draw. This is because if you take your Levo before the blood draw the test will measure the dose just taken and show a false high. If you leave longer than 24 hours the result will show a false low.

* If you take Biotin or a B Complex containing Biotin (B7), leave this off for 7 days before any blood test. This is because if Biotin is used in the testing procedure it can give false results (most labs use biotin).

These are patient to patient tips which we don't discuss with phlebotomists or doctors.

[Wilko91 in reply to SeasideSusie]

Thanks for the reply. Wouldn't have any idea about reference ranges. Its the NHS UK, so who knows what ranges they use. I will speak with my doctor next week. I have reduced to 100mg as from yesterday. So lets see how it goes.

[SeasideSusie Remembering in reply to Wilko91]

Wilko91

Wouldn't have any idea about reference ranges. Its the NHS UK, so who knows what ranges they use.

The NHS doesn't have universal ranges, it varies from lab to lab Each lab's machine has their own range, so you have to use the reference range that comes with your result. Always ask the receptionist at your surgery for a print out of your results, never ask a doctor (they don't like us having them) and never accept verbal or hand written results as mistakes can be made.

It's very likely that you don't need a reduction in dose because of the double dose of Levo you took in the 12 or so hours before your test.

[Wilko91 in reply to SeasideSusie]

Good tips. Never seen a print out. I have always had to call the receptionist for results, over the last 10 years, and actually ask for the numbers. Not good really!