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Thyroid UK
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Will I experience negative symptoms by taking 24 hour Levothyroxine break prior to blood test?

Hi, My blood test is 11am tomorrow. I haven't taken usual 150mcgm Levothyroxine today. Will I notice any ill effects? Also, taking a break from supplements prior to blood tests.

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Sy28,

It takes up to 7 days to absorb a dose of Levothyroxine so you won't have symptoms by skipping Levothyroxine prior to your blood test. You could still take Levothyroxine today and take your Levothyroxine tomorrow after your blood test.

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Thanks Clutter, I misunderstood and thought I had to stop Levo today. Do you think it's a good idea to not take B12 today?

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Sy28,

If your B12 contains biotin you should skip it.

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Thanks

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You should take today's dose but don't take tomorrow's dose until after your blood draw. Recommendation is to leave off levo for about 24 hours, you will have left yours far too long if you don't take today's dose.

Remember to fast overnight, have tonight's evening meal then wait until after blood draw for next meal, you can have plenty of water though.

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Hi, I've just taken today's Levo, many thanks for your advice. There'll be a 21.5 hours gap between now and blood test. I take your point about fasting after tonight's meal and will stick to water. Out of interest, could a heavy cold affect results - typically it developed overnight and symptoms are worsening today. Wrapped up!

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Yes, I think a heavy cold could possibly affect results. It might be an idea to cancel and wait until you're over your cold.

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Thanks, Susie, I'll cancel just to be sure. This forum is an invaluable resource!

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It would be better if you could make your next appointment for early in the morning. TSH will not be at its highest at 11 am. You'd be better off having the blood draw before 9 am, if you can. :)

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Thanks greygoose, I had a (strong) feeling you'd say that, and I agree, but unfortunately I'm not being offered any earlier appointments...for accuracy sake, I think I'm going to test privately and compare both sets of results with the GP.In principle I support the NHS, but recent experiences of two different surgeries - one in Gloucestershire, the other in Dorset - shared identical responses. Neither GP were prepared,or able, to challenge decisions set by their local Clinical Commissioning Groups. This applied to identical T3 conversations, as well as lab test requests being over-ruled. I'm really hoping my new GP's instructions to test for T3 will be upheld and we can compare notes, build a bigger picture.

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I'll keep my fingers crossed for you. :)

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