Blood test timing!

[Lozzer66]

I'm going for bloods one day next week at 7.20 am....Ive been fasting last few times and not having ndt until after test ...I usually take a dose 6am and 3pm....is it better to take the last dose a bit later on in the day or shall I just leave things as they are ?thanks

[Clutter]

Lozzer66,

Just take your morning dose after the blood test.

[Lozzer66 in reply to Clutter]

Clutter ..I was asking if my 3pm dose day before should stay at 3pm or push it to later in day?

[Clutter in reply to Lozzer66]

Lozzer66,

I don't think you need to change the time just because you're having a blood test.

[jkozlow3]

You're going to get different opinions on this. Here's mine:

Taking anything with T3 (including NDT) will cause an artificial spike of Free T3 (FT3) levels for 18-24 hours (hopefully you are getting this tested, as this is by far the most important blood test when on thyroid meds). This is confirmed by 2 studies I have read. I would therefore try to wait 18+ hours if possible. You can either take your entire dose in the AM the day before your blood work or take your afternoon dose a little earlier (although this will be tough to do on an empty stomach). Personally, I would take your entire dose in the AM the day before your blood work OR push your appointment back a little. Do NOT take any meds the morning of the test! Put your meds in a small bottle/bag and bring them with you and take them as soon as the blood is drawn. Hide your pill bottle if need be so that you don't accidentally take them out of habit when you wake up that morning!

Others may tell you that you should test anywhere from 6-8 hours after a dose to get an "accurate" reflection of the levels in your blood. Some others think that T3 meds are out of your system after 8 hours. This is not true. FT3 levels will be artificially elevated until the 18-24 hour mark. If you test before this, your doc will probably decrease your dose and you'll end up under-medicated. You can still get an accurate picture of your T3 levels if you wait 24+ hours after a dose - in fact I believe that you will get a MORE accurate picture by doing so. Here's an example:

A forum member posted that they always wait ~24 hours after a dose for blood work. On 2 grains, their FT3 value was around mid-range after 24 hours. After switching to 3 grains for awhile, their blood work showed FT3 up near the top of the range 24 hours after their last dose. As this example demonstrates, your FT3 levels increase over time - even when testing after the majority of T3 from your last dose has left your system. I believe this is the most accurate way to test.

Dr. Lowe (one of the great thyroid docs) has stated numerous times that many people/docs incorrectly assume that T3's benefits are lost once the levels decrease in your blood. T3 has a short half-life and peaks a few hours after a dose and then gradually returns to the baseline after 18-24 hours. However, Dr. Lowe has stated that the effects of a dose of T3 continue on for several days at the metabolic/cellular level, even though the blood levels don't reflect this. That's why he (and many other doctors who treat hypothyroidism in a similar fashion to Dr. Lowe) don't pay much attention to blood levels. Instead, they treat based on symptoms and metabolic levels of the patient (pulse, temperature, etc.), as they believe that this more accurately reflects how the hormone is being used by the body vs. how much is circulating in the blood. It can pour rain 24 hours a day, but if I rely on that rain for drinking water and you only give me a small shot glass to collect the rainwater in, I'm going to end up dehydrated! If I paid attention to the amount of rain that fell in a 24 hour period vs. how much I was able to collect, I would incorrectly infer that I *should* have plenty of water. This is why many docs use patient symptoms and metabolic symptoms vs. blood work. Blood work doesn't reflect what is happening at the cellular level (especially if you take blood work prematurely before the 18-24 mark after a dose)!

Hope this helps!

[Lozzer66 in reply to jkozlow3]

jkozlow3 thanks for that ...very informative ..I'm actually self medicating and just want the bloodwork for my benefit and not gps ... (I do take my temperatures and they are still low and erratic )..I have last few times left it approx 18hr but just wondered if shorter time or longer was better..thanks again