Levothyroxine dosage

[Haus66]

Is my gp correct that dosage of above medication can be based on your weight I presume as well as levels. He said normal guideline 1.5mg per kilo of body weight. I've never heard of this is this right?

[shaws Administrator]

I thought that was a rumour - just as they've been told that the TSH informs them how 'well' the patient is and don't increase despite continuing symptoms. Extract from BTA:

Levothyroxine doses are dependent upon the person’s body weight. Most patients require between 100 and 150 micrograms a day, but the dose can be lower than 75 micrograms or up to 300 micrograms a day, depending on your needs. If you have severe hypothyroidism or are at risk of heart problems you can expect your doctor to start cautiously and increase the dose gradually. Patience is needed as it can take several months before you feel better and for the thyroid function tests to return to normal or be judged satisfactory by your doctor. During this period you will have regular thyroid function tests, usually every six to eight weeks

btf-thyroid.org/information...

I would expect this response from the BTA and how many on this forum have stood on a scale to be weighed before being prescribed thyroid hormones?

Whereas Dr Skinner, Dr Peatfield and other holistic doctors treated the symptoms and stated that nowadays our doses are far too low to enable us to recover as only TSH is considered. Doses used to vary ( NDT)around 200 to 400mcg. So, is it the dose that is prescribed, in the eyes of the BTA which is king not the recovery of the patient? It must be otherwise there would be no need for this forum.

What dose of levo is required for each 1lb in weight? It doesn't make sense to me but of course I am not an Endo or qualified. Weight gain is a clinical symptom so I guess if you are dosed according to weight, as you lose excess is levo reduced to ?

The message should be 'treat the patient until he/she is relieved of all symptoms'. Thyroid hormones aren't dangerous unless we seriously overdose: are very frail with heart disease: should be offered 'options' as levo isn't the 'be all and end all' of replacements.

[SeasideSusie Remembering in reply to shaws]

"Levothyroxine doses are dependent upon the person’s body weight. Most patients require between 100 and 150 micrograms a day, but the dose can be lower than 75 micrograms or up to 300 micrograms a day, depending on your needs."

What a wonderful example of contradiction!

Dose is dependent on weight. But dose is dependent on needs.

[shaws Administrator in reply to SeasideSusie]

They definitely haven't a clue. I doubt they can join up dots at all. No wonder we're on a forum instead of relaxing somewhere eating a box of chocolates and reading a nice book and not gaining weight.

[Clutter]

Haus66,

Weight/dose ratio is more commonly used to estimate the dose required for thyroidectomised patients after surgery. Your GP may use it to estimate your initial dose but thereafter dose will be guided by your thyroid blood results.

The goal of Levothyroxine is to restore the patient to euthyroid status. For most patients that will be when TSH is 1.0 or lower with FT4 in the upper range. FT4 needs to be in the upper range in order that sufficient T3 is converted. Read Treatment Options in thyroiduk.org.uk/tuk/about_...

For maximum absorption Levothyroxine should be taken with water 1 hour before, or 2 hours after, food and drink, 2 hours away from other medication and supplements, and 4 hours away from calcium, iron, vitamin D supplements, magnesium and oestrogen.

It takes 7-10 days for Levothyroxine to be absorbed before it starts working and it will take up to six weeks to feel the full impact of the dose. Symptoms may lag behind good biochemistry by several months.

You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine. Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.

thyroiduk.org.uk/tuk/about_...

[helvella Administrator Thyroid UK]

Given:

Absorption varies across patients - and within a single patient - by quite a significant margin. (Possibly 40 to 80% of dose swallowed.)

Need varies by time of year for many.

Tablets can legitimately vary from 90 to 105% of claimed potency in the UK (though usually much better than that).

Weight is some times suggested to be the lean body mass of the individual. Sometimes not.

The dose per kilogram varies depending where you read it. Typically between 1.4 and 1.9 micrograms per kilogram (not milligrams).

Dose by weight can only ever give an estimate - which might help after total thyroidectomy rather than a pure guess. Yes, it could be used for initial dose estimation - but what is better about doing that than simply starting on the conventional 50 micrograms? (Unless they are claiming people should be started on their estimated final dose, which seems rather heavy-handed.)

[shaws Administrator in reply to helvella]

I shall have to lie down now after that explanation - my poor brain is spinning - mind you that might be a good thing