How to Calculate Percentages for Test Results?

[wkingmom]

I've seen several posters state for your thyroid test results, the rule of thumb is:

1) Free T4 to be MIDDLE of the range or slightly higher. This means to be at least 50% of the range or more.

2) Free T3 to be the middle to upper 1/3 of the range. This means 50% to 67% of the range, with most needing to lean towards the 67% of the range.

How do you calculate the percentages?

Here are my latest test results:

TSH - 0.65  Standard Range 0.3-3.0
T4 -    1.1     Standard Range 0.8-1.8
T3 -    2.5     Standard Range 2.3-4.2

Thanks in advance!

[Barb135]

As I mentioned above, you can always abbreviate FT3 and FT4... it means the same thing; just so we know.

I'm glad you were able to get the math to work out.  Math isn't my strong subject either, so I understand where you're coming from.

[wkingmom]

Thanks Barb.  I practiced the formulas and finally got the same answer you got.

And I'll be sure to reference FreeT4 and FreeT3 like you say.  Thanks!

[Barb135]

Typically, thyroid tests are done every 5-6 weeks when one is actively adjusting thyroid hormone medications.

[Barb135]

I was pretty sure the tests were Free T3 and Free T4, because the results and reference ranges are what we, typically, see, but it's very important to specify that when discussing them for the reason I mentioned above... it saves a lot of explanation when you're posting.

Practice doing the math on the Free T3 and Free T4, since doing it on the TSH is a lesson in futility... If you follow the steps I followed above, you should get the exact results I got for each step.

[wkingmom]

@flyingfool - thanks for the info about TSH, but I'm not worried about the TST test itself.  What I meant was I think I'm still doing the math wrong.

Like I said in my post above, I'm not taking any thyroid medication.  I've been taking a supplement called Thyroid-Gold for about a month now, since 2/2/2016.  It's a thyroid powder taken from New Zealand cows.  

About how long should I take this supplement before testing again to see if it's making any difference?


@Barb - it's Free T4 and Free T3.  I ordered these tests myself and made sure of that!

[Barb135]

TSH does not "ever" have to be calculated as a percentage.

Always be sure to specify FREE T3 and FREE T4, because if you say just T3 and T4 that means Total T3 and Total T4 and they aren't the same tests as the Frees.  Total T3 and Total T4 are obsolete and of little value.  You can abbreviate to FT3 and FT4, but not just T3 and T4...

[flyingfool]

TSH his of dramatically less importance.  I wouldn't worry about it too much.  WHile Dr's seem to focus on it.

TSH can vary by as much as 70% or more within a single day. So it is MUCH to unreliable to really base anything on.  It is at best a screening tool.

It is FAR more important to actually focus on the two ACTUAL Thyroid hormones T4 and T3.  And the "Free" versions of each.

Your body at the cellular level ONLY uses the Free T3 hormone. So this is what your body uses and thus it is critical as to how you feel and thus correlates best with symptoms.

Are you currently taking thyroid medication?  If so what are you taking and what dose?  How long have you been on thyroid medication and how long on the current dosage?

[wkingmom]

I think I still calculated my TSH wrong...

[wkingmom]

Okay, I got it now!  Math is not one of my strengths.  I didn't realize you were putting in my score.  Now I understand.

So my TSH is at 23% of the range,
T4 is 30% and
T3 is 11%.

Yikes.  And T3 is the best indicator, isn't it?  Last time I went and had my labs done at a private lab company because my doctor refused to do them.  About how often should I get my tests done?  

[Barb135]

When someone says 50% of T4, they mean you should be at 50% of the T4 range that your lab is using... that means in the middle of the range.  With the range your lab is using 50% or mid range would be 1.3.  That means, ideally, your FT3 should be 1.3, but it's not, it's only 1.1, which is low of the target.

I just calculated your percentages for you... that's the first calculation I did and your FT4 is at 30% of its range.

The second calculation I did is your FT3 and your FT3 is at 11% of its range... Mid range for the FT3 your lab is using is 3.25, which means that's, "ideally", the minimum your FT3 should be... yours is only 2.5, so you're considerably short of that target.  

It's difficult to get in to see good endos... my endo when out of practice in October and when I got a referral to a new one in November the soonest I could get in was the end of April, so a 4-5 month wait isn't unusual.

[wkingmom]

Thanks Barb, but I'm still confused.  I don't know what 50% of T4 is.  I don't know how to figure out what my percentage is.  How do I figure out where I am?

I am not on any medication right now.  Those results were from 1/15/2016.  Since 2/2/2016 I've been taking thyro-gold.  I have been trying to find a decent endocronologist that takes health insurance.  
I have been looking on healthgrades and vitals website and reading reviews on various endos.  There was only one endo I found that had good reviews from patients.  I have an appointment with him on June 1st.  Yep, that was his first available appointment.

In the meantime I've been trying to self medicate with thyro-gold.

[Barb135]

To calculate the percentages:

Subtract the lower reference range from the upper reference range;
Subtract the lower reference range from the result;
Divide the second result by the first result
Here's the calculation for the FT4:

1.8 - 0.8 = 1.0
1.1 - 0.8 = 0.3
0.3 / 1.0 = 0.3
Move the decimal point 1 place to get 30%


Here's the calculation for the FT3:

4.2 - 2.3 = 1.9
2.5 - 2.3 = 0.2
0.2 / 1.9 = 10.5 rounded to 11%

Try the calculations, yourself, so you can see exactly what it looks it...

Both of your levels are too low in the ranges, indicating that you need an increase in medication...however, it's not necessarily correct that FT3 needs to lean toward the 67% range.  That's an individual number and varies for all of us.  Whereas one person might need to be closer to the top of the range, another might be quite comfortable closer to the mid range mark.  This may even be different for each of us, at different times, as I seem to be finding out for myself.