Thyroid blood test with reverse T3 and key micronutrients

Secondary relevance

The broadest thyroid profile in the catalogue: it includes TSH, free T4, free T3, reverse T3, three types of antibodies and a selection of micronutrients. It is designed for people who specifically want reverse T3 measured, with a clear understanding of its significant clinical limitations.

No prescription or appointment needed

Results in 5-7 working days

Includes: TSH · Free T4 · Free T3 · Reverse T3 · Thyroid peroxidase antibodies · TSH receptor antibodies · Thyroglobulin antibodies · Selenium · Ferritin. 12 in total. See what each one measures

Secondary relevance. It is not the one I recommend to start with. It is here because it adds something in specific situations, but for most people it looks at more than is needed.

What it is for

It is designed to measure reverse T3 within a broad assessment of thyroid function, autoimmunity and nutritional status, when there is a specific clinical reason for it.

Bear in mind that reverse T3 is not part of the usual assessment of hypothyroidism and cannot on its own explain persistent symptoms when TSH and free T4 are normal. Nor should it be used on its own to decide on thyroid hormone treatment. If the aim is to review the thyroid and several micronutrients without measuring reverse T3, the closer alternative is the thyroid blood test with key micronutrients.

When it is recommended

When you specifically want reverse T3 measured in a particular clinical context
When you are looking for this test specifically and understand that its usual value is limited
It is not recommended as a first assessment of hypothyroidism or as a general explanation for persistent symptoms with normal thyroid tests

Clinical comment

Reverse T3 is not one of the tests recommended routinely to diagnose or monitor hypothyroidism. It can rise when the body adapts its metabolism to a serious illness, prolonged calorie restriction or other situations of physiological stress. That is why a high value does not, on its own, show that the thyroid is working poorly.

Nor is there enough evidence to adjust thyroid hormone treatment on the basis of this result. There are very rare situations in which a specialist may consider it as part of a specific investigation, but that does not make it a general screening tool.

Dr. Antonio Mas

What is tested

TSH: The hormone the pituitary gland uses to regulate the thyroid. It is usually the first test to change and guides the rest of the investigation.
Free T4: The main hormone produced by the thyroid, measured in its free fraction. It shows how much thyroxine is available in the blood.
Free T3: The thyroid hormone with the greatest activity in the tissues. It is particularly useful when TSH is low and possible hyperthyroidism is being investigated.
Reverse T3: An inactive metabolite of T4. It can rise during a serious illness, prolonged calorie restriction or other situations of physiological stress, but a result on its own does not diagnose a thyroid disorder.
Thyroid peroxidase antibodies (anti-TPO): Antibodies against thyroid peroxidase. Their presence supports an autoimmune origin, such as Hashimoto's thyroiditis, although they can also appear in people with normal thyroid function.
TSH receptor antibodies (TRAb): They detect antibodies directed against the TSH receptor. The stimulating ones are characteristic of Graves' disease.
Thyroglobulin antibodies (anti-Tg): They look for further signs of thyroid autoimmunity and can add information when anti-TPO is negative.
Selenium: Involved in the enzymes that convert T4 into T3 and in the thyroid's antioxidant systems.
Ferritin: Reflects iron stores. Iron deficiency can cause symptoms that are also attributed to hypothyroidism.
Zinc: Involved in the metabolism and action of thyroid hormones.
Vitamin B12: Completes the nutritional assessment and can add information about problems linked to other autoimmune conditions.
Vitamin D (25-OH): Assesses vitamin D status as part of the general nutritional assessment, not as a thyroid treatment.

How to prepare

No fasting is required.

If you take biotin supplements, which are common in hair and nail products, stop them 48 hours before, because they can interfere with several thyroid tests.

If you take levothyroxine, have the sample taken before that day's dose.

You can add

Without another needle. It is offered when you order, so you do not have to decide now.

General blood testA general blood test with full blood count, glucose, cholesterol and kidney and liver function: the basic parameters included in any general check-up.+€59.00
Coeliac disease antibodiesMeasures the antibodies used to investigate coeliac disease; for a reliable result, it must be done while you are still eating gluten.+€39.00

Related blood tests

We have other profiles in Thyroid with more or fewer tests:

The most comprehensive is not always the most useful. If you are not sure, the one we recommend to start with is Full thyroid blood test with anti-TPO antibodies.

What it is based on

The thyroid function and antibody part is based on the same clinical guidelines as the other profiles. Published reviews of reverse T3 conclude that its usual diagnostic value is limited, that the guidelines do not recommend measuring it routinely, and that there is not enough evidence to use it to guide thyroid hormone treatment. For that reason, it has secondary relevance in this protocol.

Annals of Clinical & Laboratory Science 50(3):383
Trust your Endocrinologist: Report and Recommendations on the Ordering of Reverse T3 Testing
Reviews the use of reverse T3 in clinical practice and concludes that it does not provide information that changes the management of hypothyroidism.

Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.

This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.