Thyroid Resources Community Group
We are sharing here the results of our research. Much of it is evidence-based.
Hypothyroid people whose MDs watch only their TSH level during treatment are usually doomed to remain symptomatic. Those who are receiving optimal treatment, to the point where all signs and symptoms of hypothyroidism have been relieved, have MDs who understand that TSH matters least and that the free levels of T4 and T3 matter most. The tests for those two levels should be done at each thyroid checkup.
Generally speaking, those whose FTs stay within the upper third of their ranges feel best. That's just a general "rule" however, and individual needs should be respected. Some people need slightly lower levels and others need slightly higher levels. This is what makes keeping a symptoms journal quite valuable.
To determine the percentage of your lab's range where your test result for FT4 or FT3 sits, use the following formula. The example I've used is a common lab range of .8 - 1.8 ng/dL and a blood level of .9. Substitute whatever range your particular lab uses and your blood level:
1. Subtract the bottom no. of the range from the top (1.8 - .8 = 1)
2. Subtract the bottom no. of the range from your result (.9 - .8 = .1)
3. Divide the result of calculation #2 by calculation #1 (.1 ÷ 1 = .1) and turn the result ( .1) into a percentage = 10%
~~~~~~
To determine the optimal target area of any given range, use the following formula. I've used a target of 70% on a typical FT3 lab range of 2.3 - 4.2 ng/dL in the example:
1. Subtract the bottom of the range from the top (4.2 - 2.3 = 1.9)
2. Multiply that answer by the percentage (expressed as a decimal no.) you want to determine, say 70%: (1.9 x .70 = 1.33)
3. Add the bottom number of the range to #2's answer: (2.3 + 1.33 = 3.63)
70% of the range is approximately 3.6 ng/dL
~~~~~
To easily determine the exact middle level (50%) of any range, simply add the two lab limits together and divide by 2. For example, the mid level of the free T3 range 2.3 - 4.2 ng/dL can be found by calculating 2.3 + 4.2 = 6.5 ÷ 2 = 3.25.
Always remember that the math never matters as much as how you feel while your levels are at any particular level. It may be helpful to keep a journal of how your symptoms are trending during the time between dose adjustments, so you can more easily know how to adjust at the next checkup. But...never judge what you need by either symptoms or labs alone. Both have to be taken into account as a pair in order to know.
Also remember, that even once you find your optimal dose, it still can take up to two months to feel completely well. The body's cells need time to heal from the damage that the hypothyroidism has done, and that doesn't happen immediately as soon as you start taking that final, optimal dose.
Finally, please remember that thyroid function isn't static. We can find the need for small dose adjustments to maintain optimal levels. If those dose adjustments happen in a timely manner (when labs first show the need), there's a good chance symptoms won't develop.
Generally speaking, those whose FTs stay within the upper third of their ranges feel best. That's just a general "rule" however, and individual needs should be respected. Some people need slightly lower levels and others need slightly higher levels. This is what makes keeping a symptoms journal quite valuable.
To determine the percentage of your lab's range where your test result for FT4 or FT3 sits, use the following formula. The example I've used is a common lab range of .8 - 1.8 ng/dL and a blood level of .9. Substitute whatever range your particular lab uses and your blood level:
1. Subtract the bottom no. of the range from the top (1.8 - .8 = 1)
2. Subtract the bottom no. of the range from your result (.9 - .8 = .1)
3. Divide the result of calculation #2 by calculation #1 (.1 ÷ 1 = .1) and turn the result ( .1) into a percentage = 10%
~~~~~~
To determine the optimal target area of any given range, use the following formula. I've used a target of 70% on a typical FT3 lab range of 2.3 - 4.2 ng/dL in the example:
1. Subtract the bottom of the range from the top (4.2 - 2.3 = 1.9)
2. Multiply that answer by the percentage (expressed as a decimal no.) you want to determine, say 70%: (1.9 x .70 = 1.33)
3. Add the bottom number of the range to #2's answer: (2.3 + 1.33 = 3.63)
70% of the range is approximately 3.6 ng/dL
~~~~~
To easily determine the exact middle level (50%) of any range, simply add the two lab limits together and divide by 2. For example, the mid level of the free T3 range 2.3 - 4.2 ng/dL can be found by calculating 2.3 + 4.2 = 6.5 ÷ 2 = 3.25.
Always remember that the math never matters as much as how you feel while your levels are at any particular level. It may be helpful to keep a journal of how your symptoms are trending during the time between dose adjustments, so you can more easily know how to adjust at the next checkup. But...never judge what you need by either symptoms or labs alone. Both have to be taken into account as a pair in order to know.
Also remember, that even once you find your optimal dose, it still can take up to two months to feel completely well. The body's cells need time to heal from the damage that the hypothyroidism has done, and that doesn't happen immediately as soon as you start taking that final, optimal dose.
Finally, please remember that thyroid function isn't static. We can find the need for small dose adjustments to maintain optimal levels. If those dose adjustments happen in a timely manner (when labs first show the need), there's a good chance symptoms won't develop.
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