How to get an accurate T3 reading with bloods?

[Ooohmatron]

Ive asked a similar question before, regarding blood testing for T4/T3 and realised for years I was having a blood sample done a few hours after I had taken my Levo upon waking up. People on here then said to have the bloods done that morning before taking T4, to get a more accurate reading.

Since then, I've been taking T3 for the past 10 months and trying to get the level right on that, but it raised a question for me regarding when to take the blood test to check T3.

With T3 not lasting as long in your body, about 8hrs im told, what would be the best way to check the levels of this?

For example. If i take half my T3 in the morning and the other half 8hrs in the afternoon, would taking a blood test the following morning give you an accurate reading for T3?

How would you know if your T3 is high or low, because if the half-life of T3 is 8hrs-ish, surely the t3 reading is going to be low the next morning? If I then take T3 and did a blood test a few hours later, then obviously the T3 reading will be pretty high (which it has been from previous tests done like this)

So Im just wondering, whats the best time take a blood test to get a reading for T3? If a T3 reading comes back at say 3.4, with no T3 in your system, how can you tell what its going up to once you take the T3? are we talking about taking two tests? one before and one after?

cheers

[TiggerMe]

Blood tests aren't really the best thing to go on as it obviously only shows levels in the blood rather than in the cells but it's what we are stuck with... If testing for GP/ Endo stick with the general rules to save risk of getting a dose reduction (always handy to have some in reserve if you do choose to take a little less as medics don't really understand the fine tuning needed)

Endo's often request 3 hours after T3 as they like to see the peak.... this often means you are left under replaced 🙄 if testing for yourself then you can trial various timings, I've done this and my fT3 goes from bottom of range to above top of range depending on timings but then I take a single morning dose others absorb faster hence dose splitting

general rule for testing is 24 hours after T4 and 8-12 after T3 test between 7-9am fasted, water only, best to replicate conditions for every blood test for some uniformity of results

When taking T3 it comes rather more down to symptoms and tuning in to what works best for you

[AKatieD]

I would echo what TiggerMe said. If you really wanted to know exactly what happens to your levels you would need to do a series of timed tests to make sure you capture baseline and peak levels which could vary between people and on different days.

It would be practically difficult and expensive to get two or more tests done on the same day and just about impossible on the NHS.

Although T3 is short acting, levels do build to a steady state over time if you are dosing consistently. It won't fall away to nothing after a few hours but will keep to a base level so long as you don't stretch the time out too far. Your timing would have to be more exact to capture peak levels.

By keeping it simple and testing consistently at a similar time of day before dosing, you will know your baseline level and can compare results with other people doing the same thing. That way you can get informed comment on this group and get results that are comparable over time. If you tried to compare your highest level with everyone else's lowest then commenting and concluding would be difficult.

[radd]

Ooohmatron

Suggested test timings here …..

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