serum thyroid normal ranges: If t3 and Tsh... - Thyroid UK

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serum thyroid normal ranges

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If t3 and Tsh are normal but t4 is high does it need medication . Then again ranges change from lab to lab . How much variance is permissible , By any chance due to a slight variance also if medicine is taken , does it not affect the condition badly .If TSH is with in normal range does it mean the functioning of thyroid gland is ok .If TSH and T3 OR TSH and T4 either of the combination is with in normal range does it indicate normal functioning of the gland . Or all three parameters ,that is t3 , t4 and TSH have to be normal . This is of academic interest and I hope members understand my curiosity .

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Most of us find the "normal" ranges are far too wide to be useful.

In particular, the TSH range, which is a doctor's first port of call, often goes up to around 4.2 [ranges vary from lab to lab] - but those of us who are hypo and on meds, need it to be much lower - under 2, and often less than 1. Equally, those of us on medication usually need our free T3 and free T4 to be in the top quartile of the range and would feel really ill with a result in the bottom of the range.

I understand that people who are not in medication may feel happy with results which aren't good enough for those of us who are on thryoid meds - ie they tolerate results at the lower end of the free T3 and free T4 ranges.

But it's all very individual. We need to have numbers in range AND feel well. I'm not sure one can draw generalisations.

helvella profile image

I posted this the other day:

The normal range: it is not normal and it is not a range

1. Martin Brunel Whyte

2. Philip Kelly


The NHS ‘Choose Wisely’ campaign places greater emphasis on the clinician-patient dialogue. Patients are often in receipt of their laboratory data and want to know whether they are normal. But what is meant by normal? Comparator data, to a measured value, are colloquially known as the ‘normal range’. It is often assumed that a result outside this limit signals disease and a result within health. However, this range is correctly termed the ‘reference interval’. The clinical risk from a measured value is continuous, not binary. The reference interval provides a point of reference against which to interpret an individual’s results—rather than defining normality itself. This article discusses the theory of normality—and describes that it is relative and situational. The concept of normality being not an absolute state influenced the development of the reference interval. We conclude with suggestions to optimise the use and interpretation of the reference interval, thereby facilitating greater patient understanding.

jimh111 profile image
jimh111 in reply to helvella

At last! Someone other than me and Gordon Skinner using the correct term 'reference interval'. If only patients could start using the term so doctors could begin to appreciate it is not a range. Thanks for the reference, I will read the paper later.

The other problem with the blood test results is that TSH, fT3 and fT4 are closely interrelated, part of a system. Consequently, each parameter should not be interpreted in isolation. For example a TSH > 10 is an excellent marker for primary hypothyroidism but low normal TSH, fT3 and fT4 is not normal and usually associated with quite severe hypothyroidism.

The blood tests need skillful interpretation and using the correct terminology 'reference interval' is a first step on that path.

Thank you very much for clarifying the point that all ranges are statistical averages and we can't exactly arrive at a conclusion . I personally feel it is better to set right the condition by making life style changes rather than going for medication .

what is the difference in the result of t3 and t4 and free t3 and t4 . Is it very different parameter .When a person is diagnosed as hyperthyroid or hypothyroid with the level of t4 and t3 or free t4 and t3 . Then how much variance is allowable from the so called normal ranges and observed ranges .

It depends. Symptoms? On meds (any)? Age? Sex? Vitamin levels? Other comorbidities? Individuals have a huge variety of results. See and the second part in next article

No symptoms . No medicines. No other health problems.

So why was a test done?

Routine check up . That's why the surprise and apprehension .

I'd say ignore it. If you hadn't had the checkup you would have no reason to think there was problem. More likely to be a test interference problem. If you develop symptoms over the next year, might be worth looking at. My surgery doesn't check anything routinely unless you are on meds for something. I am not a medical professional and that is just my personal opinion. You need to decide.

Thank you for a wise councel

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