Interpret your TFT results with medical accuracy. Features a clinical calculator, thyroid unit converter, user guidelines, and reference ranges from 6 sources.
TFT Test Result Interpreter & Unit Converter
Your complete clinical toolkit for evaluating Thyroid Function Tests (TFTs)
1 TFT Result Interpreter
Enter your lab values below. TSH is highly recommended for an accurate clinical assessment. Leave any untested fields blank.
Clinical Interpretation
2 Live Advanced TFT Unit Converter
Laboratories globally utilize different measurement systems (Conventional Standard vs. International SI). Type a value in either side to instantly convert your results back and forth.
* Note: TSH does not require conversion (mIU/L = uIU/mL = mU/L). Anti-TPO is standard globally at IU/mL or kIU/L.
3 Complete Reference Ranges Database
Below are the standard adult (non-pregnant) reference values utilized by global endocrinology institutions. This chart includes both US Standard Units and International System (SI) Units.
| Test Name | Standard Range (US) | SI Range (Global) | Clinical Significance |
|---|---|---|---|
| TSH | 0.4 – 4.0 mIU/L | 0.4 – 4.0 mU/L | Primary screening marker |
| Free T4 (FT4) | 0.9 – 2.3 ng/dL | 12.0 – 30.0 pmol/L | Active, unbound Thyroxine |
| Total T4 | 4.5 – 12.0 mcg/dL | 58.0 – 154.0 nmol/L | Total Thyroxine (bound + unbound) |
| Free T3 (FT3) | 2.0 – 4.4 pg/mL | 3.1 – 6.8 pmol/L | Active, unbound Triiodothyronine |
| Total T3 | 80 – 200 ng/dL | 1.2 – 3.1 nmol/L | Total Triiodothyronine |
| Anti-TPO | < 34 IU/mL | < 34 kIU/L | Autoimmune marker |
| T3RU (Uptake) | 24% – 34% | 0.24 – 0.34 (Fraction) | TBG binding site measurement |
4 Best Practices & Clinical Testing Guidelines
To ensure the absolute highest accuracy of your Thyroid Function Tests, strictly adhere to these modern clinical guidelines before your blood draw.
- Optimal Time of Day: TSH fluctuates according to your circadian rhythm and peaks in the early morning. For accurate clinical tracking and consistency, always get your blood drawn between 8:00 AM and 9:00 AM.
- Fasting Requirements: Complete fasting is not strictly mandated, but eating a large meal can mildly suppress TSH levels. If you tested fasting previously, continue to do so for a reliable “apples-to-apples” comparison.
- Levothyroxine Medication Protocol: If taking daily thyroid hormone replacement therapy, take your medication after your blood draw. Taking it directly before your test can falsely spike circulating Free T4 levels.
- The Biotin (Vitamin B7) Warning: High doses of Biotin (commonly found in hair, skin, and nail supplements) will severely interfere with standard laboratory assays. Biotin mimics Graves’ disease results (falsely low TSH, falsely high T4/T3). Cease all Biotin intake 3 to 5 days prior to testing.
- Pregnancy & Estrogen Therapy: High estrogen states drastically increase Thyroid Binding Globulin (TBG). This makes Total T4 and Total T3 appear falsely elevated. Always insist your doctor specifically orders Free T4 and Free T3 tests to bypass protein interference.
- Non-Thyroidal Illness Syndrome: Severe acute illnesses, infections, or hospitalizations can temporarily suppress your thyroid markers (Euthyroid Sick Syndrome). Routine thyroid testing should generally be delayed until you have fully recovered from acute sickness.
