Optimal Result: 71 - 180 ng/mL, or 7100.00 - 18000.00 ng/dL.

Triiodothyronine or T3 is the most biologically active thyroid hormone in humans. It is called total T3 because it includes both free T3 and T3 bound to proteins. T3 acts on almost every cell in the body by setting the metabolic rate of cells. T3 is critically important for growth and development, especially in fetuses and children. The thyroid gland produces and releases T3 into the blood; however, four-fifths of T3 is formed by the conversion of another thyroid hormone T4 (thyroxine). This takes place in the liver, kidney, thyroid, and other tissues. Free T3 is the biologically active portion of total T3. Approximately 99.5% of T3 in the serum is bound to serum proteins such as thyroxine binding globulin (TBG).

Normal Ranges for Total T3:

Adult (> or =20 years): 80-200 ng/dL

0-5 days: 73-288 ng/dL

6 days-2 months: 80-275 ng/dL

3-11 months: 86-265 ng/dL

1-5 years: 92-248 ng/dL

6-10 years: 93-231 ng/dL

11-19 years: 91-218 ng/dL















What does it mean if your Total T3 result is too low?

Decreased T3 levels in the serum usually indicate hypothyroidism or chronic or subacute thyroiditis. Any serious illness can decrease T3 levels. Abnormally low T3 may cause symptoms of hypothyroidism including weakness and fatigue, cold intolerance, shortness of breath, weight gain, constipation, cognitive problems, dry skin, hoarseness, and swelling (edema).

Some specific causes of low free T3 are:

- Hypothyroidism

- Chronic thyroiditis

- Subacute thyroiditis

- Nephrotic syndrome

- Drugs that decrease TBG (e.g. anabolic steroids, glucocorticoids)

-  High doses of biotin may cause interference with this marker

What does it mean if your Total T3 result is too high?

Elevated T3 levels may indicate hyperthyroidism, thyroid hormone resistance syndrome, or T3 toxicosis. Serum T3 levels can be expected to increase during normal pregnancy, but other tests may be necessary to rule out hyperthyroidism. Elevated T3 may cause symptoms of hyperthyroidism including excessive appetite, anxiety, heart palpitations, shortness of breath, sweating, weight loss, emotional disturbances, and intolerance to heat. 

Some specific causes of high free T3 are:

- Hyperthyroidism

- Euthyroid hyperthyroxinemia

- T3 toxicosis

- Acute thyroiditis

- Pregnancy

- Familial dysalbuminemic hyperthyroxinemia

- Drugs that increase TBG (e.g. estrogens, tamoxifen, opioids)

- Synthetic T3 treatment

10 000+ happy clients
100% satisfaction
★★★★★ customer support

Understand blood, stool, and urine medical results from your labs.

Get 10% off your plan.

Use promocode

Advanced Plan personal plan

  • Yearly subscription
  • Instant interpretation
  • We upload five reports for you
  • Use the free self-upload form
  • 2500+ biomarkers explained
  • Nutrition Recommendations
  • Online support
  • Cancel anytime

Own It For Life premium personal plan

  • No subscription
  • Unlimited access
  • Unlimited storage
  • Instant interpretations
  • We upload ten reports for you
  • Use the free self-upload form
  • 2500+ biomarkers explained
  • Nutrition Recommendations
  • Dedicated support

Pro Plan for health professionals

  • Track multiple clients results
  • No setup fees
  • No hidden costs
  • Cancel anytime
  • Instant interpretations
  • Use the free template forms
  • 2500+ biomarkers explained
  • Additional team member $25
  • Personal training and support

Healthmatters.io software for professional use.

Welcome to Healthmatters Pro.

Save time on interpreting lab results with the largest database of biomarkers online. In-depth research on any test at your fingertips, all stored and tracked in one place.

Learn More

We implement proven measures to keep your data safe.

At HealthMatters, we're committed to maintaining the security and confidentiality of your personal information. We've put industry-leading security standards in place to help protect against the loss, misuse, or alteration of the information under our control. We use procedural, physical, and electronic security methods designed to prevent unauthorized people from getting access to this information. Our internal code of conduct adds additional privacy protection. All data is backed up multiple times a day and encrypted using SSL certificates. See our Privacy Policy for more details.

General Data Protection Regulation (GDPR). HIPAA compliance for healthcare professionals

Understand Your Lab Result Now

  • Instant interpretation
  • 2500+ biomarkers explained
  • Science-based recommendations
  • Online support
  • Secure and private portal

Get 10% off with promocode: