Thyroid UK
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Diagnosed by you lot before doc

Well today I have been diagnosed with auto immune underactive thyroid, even though u lovely lot diagnosed me a month ago. the doc given me a very low dose of levothyroxine.

I Mentioned about having Ferritin, b12, and foliate, and also Adrenal function test but doc wasn't keen to test these.

Wondered how long will it take to feel some benefit from these tablets, or will I see any benefit as only on 25mg.

6 Replies

25mcg is extremely low unless you are very frail with a heart complaint. 50mcg is usually a starting dose with an increment of 25 around every 6 weeks until the patient feels 'well' not until the TSH is somewhere 'in range'. The aim should be a TSH of 1 or lower.


Frustrating that doctor wouldn't test as from what I've read here these are often low in patients with thyroid issues. I would put something in writing to that effect. If that fails I would consider making a complaint. Vit D needs to be tested as well.

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Annoying though the wait was, your GP was following protocol by waiting a few weeks after an abnormal TSH to rule out a virus or infection as the reason for elevated TSH.

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 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 but you will probably feel some improvement around weeks 2-4. 25mcg is a low dose and will almost certainly need increasing.

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.

Most people will find symptoms resolve after their TSH drops to around 1.0 with FT4 in the upper range but symptoms can lag a couple of months behind good biochemistry.

Positive thyroid peroxidase antibodies means you have autoimmune thyroid disease (Hashimoto's) which causes 90% of hypothyroidism.  100% gluten-free diet may improve symptoms and reduce antibodies.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thanks for the info and advice. Much appreciated x


Your Levo will only work well in your body when Ferritin - folate - B12 - VitD are at a good level.  So have them tested as soon as possible ....

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Positive antibodies also mean that you will probably need an increasing dose over the next months and years as your thyroid is progressively destroyed, so don't think your are nagging your doctor if you go back every 6 months or so to get an increasing dose if your symptoms reappear.


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