What Should a Full Thyroid Panel Include for Fatigue?

For fatigue, the thyroid tests worth getting are TSH and free T4, plus TPO antibodies to show whether Hashimoto's, an autoimmune attack on the thyroid, is the cause. Free T3 rarely helps when the thyroid is underactive, and the American Thyroid Association says reverse T3 is not clinically useful in healthy people outside the hospital. Thyroid trouble and perimenopause cause many of the same symptoms, so check your thyroid before you decide your tiredness comes with age.

Which thyroid tests should I ask for if I'm always tired?

TSH, free T4 and one antibody test cover what a tired woman needs to know. According to the American Thyroid Association's guide to thyroid tests, positive TPO or Tg antibodies in someone with an underactive thyroid confirm Hashimoto's. The same guide says tracking antibody levels over time doesn't show whether you're getting worse or responding to treatment, so one test is enough.

A positive TPO result on its own isn't a diagnosis. Many people with TPO antibodies have a thyroid that works normally. If your antibodies come back positive and your TSH and free T4 are normal, that's a reason to keep an eye on your thyroid.

Reverse T3 is the one you can leave off. No professional guideline recommends testing it, and when one hospital reviewed its orders, 11 of 20 reverse T3 tests looked inappropriate. Reverse T3 might help in one situation: women already on thyroid medicine who still feel hypothyroid. That idea comes from one small clinic study of 98 tired patients. Very few patients in that study who weren't on thyroid medicine had a high reverse T3, so the authors didn't recommend the test for them.

What can mess up thyroid test results?

• Biotin. This supplement is in many hair, skin and nail gummies, and it can make thyroid results look abnormal when they're normal. The American Thyroid Association says to stop biotin 2 days before your blood draw.
• Your lab's biotin rule. Labcorp's prep instructions for its thyroid panel go further and recommend waiting at least 72 hours after your last biotin dose. Follow whatever your lab asks.
• Birth control pills and other estrogen. Estrogen raises total T4 and total T3 because it increases the proteins that carry thyroid hormone in your blood. If you take the pill or estrogen, ask for TSH and free T4 rather than total T4. The ATA says TSH and free T4 are the better tests here, and they're typically normal.
• Starting or stopping oral estrogen while on thyroid medicine. Oral estrogen can raise the dose of thyroid hormone you need. If you already take thyroid medicine, recheck TSH 6 to 8 weeks after you start or stop oral estrogen.

What if my TSH is only a little high?

Repeat the test before anyone treats it. A mildly high TSH often comes back normal on its own. If your TSH is high and your free T4 is normal, the usual advice is to confirm it with a second test. Retest after 1 to 3 months if TSH is under 15 mIU/L, or after 1 to 2 weeks if it's 15 or higher.

A mildly high TSH with a normal free T4 is called subclinical hypothyroidism. Within 5 years, almost two thirds of cases go back to normal thyroid function.

Whether to treat it depends on more than the number. Expert guidelines suggest considering treatment when TSH is above the upper limit of normal but under 10 mIU/L and you also have hypothyroid symptoms, positive TPO antibodies or heart disease risk. They also suggest considering it when TSH is over 10.

A normal TSH on thyroid medicine doesn't always mean you feel better. About 15% of people on T4 replacement with a normal TSH still report fatigue and other hypothyroid symptoms. If treatment doesn't bring lasting relief, your clinical team should look for other explanations. Stopping levothyroxine can be considered if your TSH was under 7 mIU/L before you started.

How much does a full thyroid panel cost?

Labcorp's panel covers the three markers that matter for fatigue, plus free T3. The instructions ask you to fast for 12 hours before the draw, and the biotin wait above applies too. The panel doesn't include reverse T3, and you don't need to add it.

What if my thyroid tests are normal and I'm still exhausted?

In most healthy people, a normal TSH means the thyroid is working properly. A normal TSH and free T4 rule out the most common thyroid explanation for your tiredness.

Normal results don't mean your fatigue is age. Fatigue, poor sleep, mood changes, skin and hair changes, cycle changes and heat intolerance show up with thyroid disease and with the menopause transition. That's why the two get mixed up between 40 and 60. Once your thyroid is ruled out, the hormones that shift in your 40s are the next place to look. Bring your results to your clinical team along with how your sleep, cycle and mood have changed.

Some women are more likely to have thyroid trouble. Your risk is higher if you have a family history of thyroid disease, had postpartum thyroiditis, were treated for Graves disease or have another autoimmune condition such as type 1 diabetes. If any of those apply, ask your clinical team how often to recheck.

If your thyroid checks out and you still run out of energy by mid-afternoon, take the quiz. Tell our clinical team about your energy, sleep and cycle, and see which plan fits your goal of feeling like yourself again.