Reverse T3 and free T3; supplementary thyroid diagnostics.
Blood collection at collection point
After your order you receive instructions by email
Make an appointment at a collection point near you
Blood collection at 1,000+ locations across the Netherlands
Reverse T3 (rT3) is an inactive form of the thyroid hormone triiodothyronine (T3), produced as a byproduct of the normal metabolism of T3. Free T3 (FT3), in contrast, represents the active form of T3 that is available for use by the body. Together, these biomarkers provide important information about thyroid function and metabolism.
Testing both rT3 and FT3 is useful for a more comprehensive assessment of thyroid function, especially in cases where patients exhibit symptoms of thyroid abnormalities, but standard tests do not offer a clear diagnosis. This test is particularly helpful for distinguishing between different types of thyroid dysfunction and for optimizing treatment.
The ratio between rT3 and FT3 helps assess thyroid activity and metabolism. An imbalance may indicate a condition, such as conversion disorder, where the body has difficulty converting T4 to the active form T3, or "Low T3 Syndrome".
A high rT3 level combined with a low FT3 level may indicate decreased thyroid function or a body reaction to stress, illness, or malnutrition. This may point to the necessity of further evaluating thyroid function and potentially adjusting the treatment strategy.
A low rT3 level together with a high FT3 level may indicate hyperthyroidism or an overactive thyroid. This requires further evaluation and possible adjustment of treatment to normalize thyroid function.
The scientific support for this test within mainstream Dutch healthcare is limited. The test is not included in NHG/FMS standard guidelines.
Rationale for this test
De bepaling van reverse T3 (rT3) en vrij T3 (FT3) heeft een beperkte wetenschappelijke onderbouwing binnen de Nederlandse reguliere zorg. Deze testen zijn niet opgenomen in de standaard schildklierdiagnostiek volgens NHG- of FMS-richtlijnen. De klinische betekenis van de rT3/FT3-verhouding en concepten zoals 'conversiestoornis' of 'Low T3 Syndrome' zijn niet gevestigd in de reguliere Nederlandse endocrinologie. Voor standaard schildklierdiagnostiek volstaan TSH, FT4 en eventueel totaal T3.
Dutch clinical guidelines and healthcare organisations
International scientific literature
We recommend consulting these independent sources before ordering a preventive health check.
Brochure on preventive health checks: careful choice, reliability, pros and cons, checklist.
Independent information about preventive health checks from the National Institute for Public Health and the Environment.
Reliable patient information about illnesses and complaints from Dutch GPs (NHG).
Public-facing website of the Dutch Society for Clinical Chemistry with explanations of blood tests and laboratory values.
Practical information
After ordering we generate a referral letter and email you the instructions. You pick a collection point yourself and book an appointment there. Blood is drawn at the location, processed at the lab, and your result arrives digitally.
Often within a few working days. How soon you can be seen depends on how busy the location is and the type of analysis. For specialist analyses we first ship collection materials, which takes a bit longer.
At most collection points yes. Some accept walk-ins. This is clearly indicated per location. You choose the location that works best for you.
That depends on the test. Whether fasting is required, and from what time, is clearly stated in the instructions you receive after ordering. No surprises at the counter.
It varies per analysis: from same-day to a few working days. Standard values often come back quickly; analyses that go to an external lab can take a bit longer. You receive your laboratory report securely by email. It lists the measured values, units, reference ranges and any flags added by the laboratory.
We work with 1,000+ collection points across the Netherlands. After ordering you'll see which locations near you are available and you pick where you'd like to go.
“Very positive experience”
From ordering to having my blood drawn, everything went smoothly and was well organised. I really appreciated being able to visit a blood collection location in my own town so quickly. I received clear instructions beforehand, and the results arrived promptly by email too. Very satisfied!
“Good communication”
This company responds to questions thoroughly and promptly. The entire process, from requesting the test to having blood drawn and receiving the results, runs very smoothly. Overall, I am very satisfied!
“Wide choice of tests, fast and affordable”
You can choose the tests yourself. Fast delivery and processing, clear instructions and affordable.
“I am satisfied with the service”
I received a referral by email, just like from a GP. I did not have to send anything by post and could quickly visit a local blood collection centre. The results were fast and clear. The price was good, not too expensive, and all messages were secure.
“A very good experience”
A very good experience! I received quick answers to my questions, a custom blood test was put together, everything was arranged smoothly, and I could have my blood drawn by a healthcare professional nearby. The results were available within a few days. In short, very satisfied!
“Very good customer service”
The customer service is very good. I had a complex request, which caused an issue at the blood collection centre. Customer service resolved it very well. They also offer a wide range of tests at a reasonable price.
“Everything was well organised”
Everything was well organised. The products were delivered within a few days and, after sending in the samples, the results arrived within a few days too. Communication and information throughout the process were clear and friendly.
“Fantastic service”
Fantastic service! Very good customer service that responds quickly and thinks along with you. Good prices. I will definitely use BloedCheckup's services again.
“Very happy to have found this business”
Very happy to have found this business. We need to check our blood more often :) The process was easy. They sent me the kit at home, then I had to go to a clinic with the papers and they knew what they had to do. I got the results in less than a week.
“Smooth process and good support”
Amazing website experience. I ordered various tests for 2 people. We went to one of the supported centers and took samples. Also after the results were ready, I needed a letter from the laboratory and they prepared the letter for me in no time. Definitely recommended.
“Amazing service!”
Received a packet with everything needed, went to a walk in clinic (Amsterdam DC Clinic) where my blood was drawn and I was out the door within 5 minutes, and then after posting the samples, received results 2 days later. Results were easy to understand as well. Amazing service, would highly recommend!
“Great customer service”
I ordered a test through bloedcheckup.nl but later realized I no longer needed it. I contacted their support team, and they were very quick, responsive, and helpful in handling my cancellation. The whole process was smooth and efficient. Great customer service!