An underactive thyroid causes tiredness, weight gain, cold intolerance and heavy periods, and an overactive one causes the opposite. TSH is the test that finds both. Treatment is adjusted every 6 to 8 weeks until the level is right. The Core panel including thyroid is £350.
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Any of these needs to be seen the same day. If you are severely unwell, go to your nearest emergency department or call 999.
The thyroid sets the pace of the body. An underactive gland slows everything, producing tiredness, weight gain, cold intolerance, constipation, dry skin and heavy periods. An overactive one speeds it up, producing weight loss, tremor, palpitations, heat intolerance and anxiety.NICE NG145, 2019
It is common and it is commonly missed, because every symptom on that list has several other explanations. That is the argument for measuring rather than reasoning about it.British Thyroid Association BTA statement, 2023
The commonest cause of an underactive thyroid in the UK is an autoimmune condition where the body’s own antibodies attack the gland. It runs in families and it becomes more common with age, particularly in women.NICE NG145, 2019
An underactive thyroid raises cholesterol, and treating the thyroid lowers it. That is why a raised cholesterol is not treated as a lipid problem until thyroid function has been checked.NICE NG238, 2023
Heavy periods are a common presentation of an underactive thyroid in women, and the two are investigated together rather than separately.NICE NG88, 2021
Send us what you are seeing and we will tell you what it is likely to be.
TSH is the first test and in most cases the only one needed. Where TSH is abnormal, free T4 is added, and free T3 where the picture suggests it. Antibodies are checked once, to establish the cause, not repeatedly.NICE NG145, 2019
Ferritin and a full blood count go in the same draw, because iron deficiency produces the same tiredness and the same hair shedding and the two often sit together.Gut Snook, 2021
A neck lump is examined and, where it is not clearly nothing, imaged. A rapidly growing lump, a hoarse voice lasting over 3 weeks or difficulty swallowing goes on an urgent pathway rather than into a thyroid clinic.NICE NG12, 2015
Watching a borderline result
A mildly raised TSH with normal T4 and no symptoms is often repeated in 3 months rather than treated. A proportion return to normal on their own.NICE NG145, 2019
Levothyroxine replacement
The standard treatment for an underactive thyroid. Started at a dose set by age, weight and heart history, then adjusted every 6 to 8 weeks until TSH sits in range.British Thyroid Association BTA statement, 2023
Combination or natural desiccated preparations
Sought by some people whose symptoms persist on standard treatment. The professional position is that the evidence does not support routine use, and where they are considered it is a specialist decision with monitoring.British Thyroid Association BTA statement, 2023
Treatment for an overactive thyroid
Medication, radioiodine or surgery, decided by the cause and by your own circumstances. That is a specialist decision and it is referred rather than started here.NICE NG145, 2019
Correcting iron alongside
Where ferritin is low as well, both are treated. Treating one and not the other leaves half the tiredness in place and makes the treatment look like it has failed.New England Journal of Medicine Camaschella, 2015
TSH takes 6 to 8 weeks to settle after a dose change, so it is not rechecked before then and a level measured at 3 weeks measures nothing usable. Reaching the right dose usually takes 2 or 3 adjustments.British Thyroid Association BTA statement, 2023
The inconvenient half. A proportion of people with a normal TSH on treatment still feel unwell. That is a real experience with no agreed explanation, the evidence does not support routinely switching preparations for it, and the honest answer is to look again at iron, vitamin D, sleep and mood rather than to promise a different tablet will fix it.British Thyroid Association BTA statement, 2023
Cholesterol usually falls once an underactive thyroid is treated, so a lipid result taken before treatment is repeated afterwards rather than acted on.NICE NG238, 2023
Take the blood in the morning and before your levothyroxine dose if you are on one. TSH varies through the day and a level taken shortly after a dose reads differently, which is enough to change a decision about your dose.British Thyroid Association BTA statement, 2023
Stop biotin supplements 3 days before the test. Biotin interferes with the laboratory method for thyroid tests and can produce results that look like an overactive thyroid when nothing is wrong. Hair and nail supplements are the usual source.NICE NG145, 2019
Ask for the actual TSH number and the reference range rather than for a normal or abnormal. A TSH at the top of the range with symptoms is a different conversation from one in the middle, and you cannot have it without the figure.NICE NG145, 2019
Do not buy reverse T3 testing. It is sold as part of comprehensive thyroid panels, no professional body recommends it, and the results lead people towards treatments they do not need.British Thyroid Association BTA statement, 2023
Do not buy repeat antibody testing. Antibodies are measured once to establish the cause and the number does not guide treatment afterwards, so repeating it is a test that changes nothing.NICE NG145, 2019
Do not buy a thyroid panel every 3 months on a stable dose. Once TSH is settled, every 12 months is the interval, and more frequent testing produces variation people then treat.British Thyroid Association BTA statement, 2023
Step 1
TSH, ferritin, full blood count, lipids and liver in one draw, taken in the morning and before any dose.
Step 2
The neck examined, the number given to you with its range, and the decision made on both rather than on either alone.
Step 3
A dose change and a recheck at 6 to 8 weeks, repeated until the level sits where it should. Most people need 2 or 3 rounds.
Ask before you book if you are not sure this is the right appointment.
Tiredness, weight gain, feeling the cold, constipation, dry skin, hair shedding, low mood and heavy periods. Every one of those has other explanations, which is exactly why the diagnosis is made on a blood test rather than on the pattern.
TSH first, and in most cases that is the only one needed. Where TSH is abnormal, free T4 is added, and free T3 where the picture calls for it. Antibodies are measured once to establish the cause rather than repeatedly.
Every 6 to 8 weeks after a change, because TSH takes that long to settle. A level measured at 3 weeks measures nothing usable. Once the dose is stable, an annual check is the right interval rather than every few months.
That is a real and common experience with no agreed explanation. The evidence does not support routinely switching to combination or desiccated preparations for it. The more useful next step is looking again at iron, vitamin D, sleep and mood, which frequently explain part of it.
The Core panel including TSH, ferritin, full blood count, lipids and liver is £350. The Advanced panel with free T4, free T3, iron studies and hormones is £650. A 30 minute appointment is £150 and dose reviews by telephone are £59 each.
Stop biotin 3 days before. It interferes with the laboratory method and can produce results that look like an overactive thyroid when nothing is wrong. Hair, skin and nail supplements are the usual source and people rarely think to mention them.
No. It appears in comprehensive thyroid panels sold privately, no professional body recommends it, and the results push people towards treatments they do not need. We will not run it, and that costs us the larger panel fee.
This page is general information about a condition and it is not a diagnosis. Treatment depends on what a doctor finds when they examine you, and no outcome is guaranteed. If you are severely unwell, or if any of the warnings at the top of this page apply to you, go to your nearest emergency department or call 999.
British Thyroid Association
Management of primary hypothyroidism, statementBTA statement, 2023
Gut, British Society of Gastroenterology
Guidelines for the management of iron deficiency anaemia in adultsSnook, 2021
New England Journal of Medicine
Iron deficiency anaemiaCamaschella, 2015
NICE
NICE
Thyroid disease, assessment and managementNG145, 2019
NICE
Heavy menstrual bleeding, assessment and managementNG88, 2021
NICE
Cardiovascular disease, risk assessment and reduction, including lipid modificationNG238, 2023
Written by the clinical team at The Wellness. Awaiting clinical sign off.
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