Home › Biomarkers › TSH
According to a European guideline, people older than 65 with a TSH between 0.1 and 0.39 mIU/l have a higher risk of a form of irregular heartbeat.[1]
On this page you can read what TSH is, what the guidelines say about a value that is too low or too high, what affects your value and which other values are best read alongside it.
Also known as: thyrotropin, thyroid-stimulating hormone. At the lab: TSH.
TSH is a hormone made by your pituitary gland, a small gland in your brain, and it tells your thyroid how much thyroid hormone to make. Another name for it is thyrotropin. Your thyroid is a small, butterfly-shaped gland at the front of your neck. Your thyroid hormones control how your body uses energy and affect things like your heart rate, your weight, your digestion and your mood.[2]
If there is too little thyroid hormone in your blood, your pituitary gland makes more TSH, so your thyroid starts working harder. If there is too much, your pituitary gland makes little or no TSH. This way, your TSH shows whether your thyroid is making the right amount of hormone. A TSH that is too high or too low can point to a problem with your thyroid, but the level does not show what the cause is.[2]
TSH is measured in a small amount of blood taken from a vein in your arm. Your TSH can also be high or low while your thyroid is healthy. For example, a serious illness that has nothing to do with your thyroid can lower your TSH for a short time. In people over 80, the value can be higher without anything being wrong with the thyroid.[2]
If your thyroid makes too much hormone, many functions in your body speed up. You may, for example, have a fast or irregular heartbeat. You may feel restless or irritable, sleep badly, be tired or sweat a lot.[2]
If your thyroid makes too little hormone, everything slows down instead. You may feel tired, put on weight, feel cold easily or get dry skin. Because this happens slowly, many people notice nothing for months or even years.[2]
Adults over 60 may have different symptoms from younger people. For example, they may have less appetite or withdraw from others.[2]
Your TSH can tell you something even within the normal range. In a Norwegian study, women with a TSH between 2.5 and 3.5 mIU/L had a higher risk of dying from a heart condition than women with a TSH between 0.50 and 1.4 mIU/L. In men, that link was not clear enough.[3]
Labplusarts, the lab BioProfile works with, uses a reference value of 0.27 to 4.2 mu/l for TSH. The lab calls a value between those limits normal.[4]
| TSH | What it can point to | Who it is for |
|---|---|---|
| Below 0.1 mIU/l[1] | Markedly low (grade 2), with a higher risk of an irregular heartbeat, heart problems and broken bones | People whose free thyroid hormones are within the limits |
| Below 0.1 mIU/l[1] | A chance that the thyroid starts working clearly too hard | People younger than 65 with symptoms |
| 0.1 to 0.39 mIU/l[1] | Mildly low (grade 1), with a higher risk of a form of irregular heartbeat | People older than 65 |
| 0.1 to 0.39 mIU/l[1] | Mildly low (grade 1), with a small chance that the thyroid starts working clearly too hard | Younger people without symptoms |
Source: European Thyroid Association, guideline on a TSH that stays too low while the free thyroid hormones are within the limits.[1]
A TSH that is too low can point to a thyroid that works too hard. If your TSH stays too low while your free thyroid hormones are within the limits, the European guideline calls this a mild form of it. According to the guideline, a TSH below 0.1 mIU/l comes with a higher risk of an irregular heartbeat, heart problems and broken bones.[2, 1]
A TSH that is too high can point to a thyroid that works too slowly. A doctor will then often request other thyroid tests to find the cause. In a Norwegian study, a TSH in the upper part of the normal range, between 2.5 and 3.5 mIU/L, was also linked in women to a higher risk of death from a heart condition.[2, 3]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
If you are pregnant, this affects your TSH. In the first three months, your TSH is often a little lower. If you have had a thyroid problem before, talk to your doctor when you are pregnant or want to become pregnant.[2]
For this test you sometimes need to stop certain medicines, so tell your doctor everything you take. Never stop a medicine on your own, only when your doctor tells you to. If you take thyroid hormone as a medicine, your TSH is measured regularly to check that the dose is right.[2]
A condition in which your immune system targets your thyroid is the cause seen most often when the thyroid works too hard or too slowly. Sometimes the cause of a TSH outside the range lies in your pituitary gland, but that does not happen often.[2]
TSH is included in BioProfile 87, 121 and 150.[5]
The BioProfile editorial team wrote this page on 29 October 2026 from the sources below, which we read on 29 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert is still reviewing this page; once that review is done, the expert's name and the date of the review will appear at the top. This page explains and does not diagnose. Discuss a value outside the range with your GP.
