Thyroid Function Calculator

Enter your TSH, Free T4, and Free T3 lab values into the Thyroid Function Calculator to evaluate whether your thyroid hormone levels fall within normal ranges. Select your test type and age group, and get back a clear status interpretation (normal, high, or low) for each marker — plus an overall thyroid function assessment. Always follow up with your doctor for a clinical diagnosis.

Disclaimer: This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any health-related decisions.

Select your age group to apply the correct reference ranges.

mIU/L

Normal adult range: 0.4 – 4.0 mIU/L

ng/dL

Normal adult range: 0.8 – 1.8 ng/dL

pg/mL

Normal adult range: 2.3 – 4.2 pg/mL

µg/dL

Normal adult range: 5.0 – 12.0 µg/dL

Results

Overall Thyroid Function Assessment

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TSH Status

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Free T4 Status

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Free T3 Status

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Your TSH Value

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Your Free T4 Value

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Your Free T3 Value

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Results Table

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Frequently Asked Questions

What information do I need to use this Thyroid Function Calculator?

You need your thyroid lab results from a blood test. At minimum, enter your TSH (Thyroid Stimulating Hormone) level and Free T4 value. Free T3 and Total T4 are optional but improve the assessment. You can find these values on your lab report from your doctor, hospital, or an at-home thyroid test kit.

Which thyroid tests can be analyzed here?

This calculator evaluates TSH (Thyroid Stimulating Hormone), Free T4 (Free Thyroxine), Free T3 (Free Triiodothyronine), and Total T4. These are the most commonly ordered thyroid panel tests and together provide a comprehensive picture of thyroid function.

What do TSH, T3, and T4 actually measure?

TSH is produced by the pituitary gland and signals the thyroid to make hormones. A high TSH often indicates the thyroid is underactive (hypothyroidism), while a low TSH can suggest overactivity (hyperthyroidism). T4 (thyroxine) and T3 (triiodothyronine) are the actual thyroid hormones that regulate metabolism, energy, and body temperature.

Can this calculator provide a thyroid diagnosis?

No. This tool is for informational and educational purposes only. It compares your lab values against established reference ranges but cannot diagnose hypothyroidism, hyperthyroidism, or any other condition. Always consult your doctor or an endocrinologist to interpret your results in the context of your full medical history and symptoms.

Why are reference ranges different for children and newborns?

Thyroid hormone levels vary significantly by age, especially in newborns and infants. Cord blood and neonatal TSH levels are naturally much higher than adult levels. The calculator adjusts the normal reference ranges based on your selected age group to provide a more accurate assessment.

Where can I find my thyroid lab results?

Your thyroid lab results are typically found on the report provided by your doctor after a blood draw, through your healthcare provider's patient portal (e.g., MyChart), or on the results sheet from an at-home thyroid test. Look for values labeled TSH, Free T4 (FT4), Free T3 (FT3), or Total T4.

What should I do if my thyroid levels are outside the normal range?

If this calculator flags any of your values as high or low, schedule an appointment with your doctor or an endocrinologist. Do not start, stop, or adjust any thyroid medication based solely on this tool. Your doctor may order additional tests (such as thyroid antibodies or an ultrasound) before making any treatment decisions.

Is my data safe when using this calculator?

All calculations are performed entirely in your browser. No personal health information or lab values you enter are stored, transmitted, or shared with any third party. Your data remains private on your own device.