What causes high FT4 thyroid and low TIBC?

High FT4 thyroid and low TIBC can be caused by many reasons.

If your FT4 thyroid is in between 0.89 ng/dL and 1.76 ng/dL and your TIBC is in between 250 mcg/dL and 450 mcg/dL then you need not worry as these are the normal ranges for FT4 thyroid and TIBC respectively. But if your levels are lesser or greater than the above values, then there may be some problem in your body.

Some examples of conditions that can increase or decrease FT4 thyroid levels include:

• Autoimmune disease
• A non-functioning thyroid gland
• Thyroiditis
• Diabetes
• Liver disease

Normal range of FT4 thyroid : 0.89 - 1.76 ng/dL

Ideal values of FT4 thyroid depending on age :

Age	Ideal FT4 thyroid value
<5 years	0.92302
5-10 years	0.95726
10-15 years	0.99277
15-20 years	1.0296
20-25 years	1.0678
25-30 years	1.10742
30-35 years	1.14851
35-40 years	1.19112
40-45 years	1.23531
45-50 years	1.28114
50-55 years	1.32867
55-60 years	1.37796
60-70 years	1.42908
70-80 years	1.4821
80-90 years	1.53709
90-100 years	1.59412
>100 years	1.65326

*Ideal values are calculated based on our database of patient records

Normal range of TIBC : 250 - 450 mcg/dL

Ideal values of TIBC depending on age :

Age	Ideal TIBC value
<5 years	259.275
5-10 years	268.894
10-15 years	278.87
15-20 years	289.216
20-25 years	299.946
25-30 years	311.074
30-35 years	322.615
35-40 years	334.584
40-45 years	346.997
45-50 years	359.871
50-55 years	373.222
55-60 years	387.069
60-70 years	401.429
70-80 years	416.322
80-90 years	431.768
90-100 years	447.787
>100 years	447.171

High FT4 thyroid and low TIBC can be caused by a lot of reasons. If you take FT4 thyroid and TIBC blood tests and the results are higher than 1.76 ng/dL for FT4 thyroid and lower than 250 mcg/dL for TIBC, your physician may recommend more tests to figure out the problem. You might also get these tests if your physician thinks you have some other disease.

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How the FT4 thyroid and TIBC Tests Are Done :

If your doctor wants FT4 thyroid and TIBC tests on you, you may need to go through these tests. During the FT4 thyroid and TIBC blood tests, a pathologist will put a needle into your veins and take out a small quantity of blood. A pathologist is a physician in the medical field who thoroughly studies the causes and effects of disease. Within a few hours you will get your FT4 thyroid and TIBC Test reports by your pathologist.

Medical References

• MedlinePlus – Thyroxine (T4) Test
• Cleveland Clinic – T4 (Thyroxine) Test: What It Is, Function, Purpose & Levels
• MedlinePlus – Free T4 test
• WebMD – What Is a Thyroxine (T4) Blood Test?
• Mayo Clinic – Hypothyroidism (underactive thyroid) - Diagnosis and treatment