Choose a test
Search by test, marker, or how you feel. Panels and at-home kits too.
No preparation for most people
Nothing to do ahead of time. Water is fine.
Free T4
What the thyroid itself is producing, as opposed to what the pituitary is asking for. The second look after TSH.
Often checked for
Thyroid follow-upMedication check-insFollowing a TSH resultTired all the timeWeight change
A quick lab visitBlood
$43
Paid at checkout. Nothing due at the lab.
Not approved? Full refund.
Not available in NY, NJ, RI, AZ, OK, MA, or PA.
What to expect
Blood draw
A standard blood draw at the lab. A phlebotomist collects it at your visit.
Results in 1 to 3 days
Typical turnaround after your visit. You get a notification the moment they land, and your dashboard shows each number next to the lab’s reference range, in plain language.
Any of 2,000+ lab locations
Walk in or book ahead. Your signed lab order works at any location that runs this test. No lab visits in NY, NJ, RI, AZ, OK, MA, or PA.
Ask about this test
What do you want to know?
AI-generated. For information only, not medical advice or a diagnosis.
About this test
Free T4 is the thyroid hormone thyroxine in its free, unbound form; the body converts it to the more active T3. TSH tells you what the pituitary is asking for; Free T4 shows what the thyroid is actually producing in response.
It is most useful when TSH is out of range or borderline, and for following thyroid medication. Illness, pregnancy, and some medicines move it, so it is read with TSH rather than alone.
Reading your result
Free T4 falls when the thyroid underproduces and rises when it overproduces. Thyroid medication moves it directly, and the timing of a dose before the draw can nudge it.
Pregnancy, severe illness, and some medicines (biotin, amiodarone, steroids) shift the result, so it is read with TSH and your medication list. On thyroid medication, the timing of the dose relative to the draw can shift the number.
Or collect at home
Kits you collect yourself and mail back to the lab. Ships free, both ways.
How it works
02
A clinician reviews it
They sign the lab order when it is appropriate. If not, a full refund.
Visit a lab, or test at home
Walk into one of 2,000+ labs, or a kit ships to your door.
04
Results in your account
Beside the lab’s reference ranges. Yours to keep and share.
Lab Pass
Test often? One flat fee for every review.
Lab Pass replaces the $15 clinician review fee on each request with one membership: $15 a month or $150 a year, however many tests you order.
TSHAny test on the menu$40
Clinician reviewIncluded with Lab Pass$15$0
Real science, real answers
Clinical-grade, start to finish.
Every order is reviewed by a licensed clinician, and every test runs at a CLIA-certified laboratory.
CLIA-certified labs
Every available lab is certified under the Clinical Laboratory Improvement Amendments, meeting both state and federal standards with regular independent inspections.
Clinician-reviewed reports
Every result is reviewed by an independent, board-certified physician licensed in your state.
Rigorous quality assurance
Every lab we use runs regular internal quality checks, participates in proficiency testing, and complies with all federal and state lab regulations.
HIPAA-compliant, always
Your health data is encrypted at bank-grade standards. We never sell it, never share it without your consent.
Questions
Before you order.
The things people ask most. Anything else, our care team answers by phone, text, or email.
No. Tell us what you want tested, and a licensed clinician in your state reviews your order. When it’s appropriate, they sign a lab order that works at any of the listed locations for this test.
Everywhere lab tests are informational and don’t diagnose conditions on their own. Available to adults 18 and older; test availability varies by lab location. Talk with your care team about what your results mean for you. Orders are reviewed and, when appropriate, signed by a licensed clinician in your state. If a test isn’t approved, you receive a full refund. All testing is performed at CLIA-certified laboratories. Your results are private and protected. Everywhere is not for emergencies: if you think you may be having a medical emergency, call 911 or go to the nearest emergency room.