Thyroid UK
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Recent Diagnosis & B12

Hi I have just been diagnosed with an under active thyroid (sorry don't have the results to publish). My GP has started my on 50mg of Levo per day and I am back in 4 weeks for another round of bloods. My GP also told me that although my vitamin B12 level was 'normal' it was in the low end therefore it would be beneficial to take a B12 supplement. Could anyone advise/recommend a decent supplement? Also I have experienced slight diarrhoea since starting the Levo, is this normal? Many thanks and I look forward to reading all the posts on this site!

3 Replies


People may expect a variety of side effects when they start Levothyroxine. They usually resolve within a couple of weeks. If not, discuss with your pharmacist and ask whether an alternative make can be tried because sometimes the fillers cause upset. There are 3 makes Mercury Pharma, Actavis (also known as Almus) and Wockhardt 25mcg.

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.

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.

Jarrows Formula and Solgar are good B12 sublingual lozenges. BetterYou Boost B12 is an apricot flavoured spray. It's a good idea to supplement a B Complex Vitamin too.


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.


Its not normal to have an upset stomach but a few people do react (and a tiny minority react to the fillers), but it usually settles down. If it doesn't then go back to your GP because there are other brands out there, and a liquid form of thyroxine too. Make sure you take your levo on an empty stomach with just water, and wait an hour. Caffeine, and calcium (which is in pretty well everything) bind to the levo making it unavailable.

Your best bet for B12 is something like Jarrow sublingual lozenges. You can get them on Amazon. Also take a general B complex to balance out your B's.

Hats off to your GP for realising that 'in range' isn't necessarily optimal.


Many thanks for the replies, I have been taking the tablet on an empty stomach but have been having the morning coffee within about half an hour, I will change that now and leave it a good hour! The GP I saw was very good, I will look for the B12 and B vitamins on Amazon, thank you!


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