What medication do I stop before blood tests?

[Mum23girls]

Having blood tests for thyroid function. I know not to take my levothyroxine before the test, but do I also need to stop vitamin b2? I take 400mg B2 and 80mg Propanalol to help prevent migraines, not sure if they will interfere with results? Thanks

[SeasideSusie Remembering]

Mum23girls

Last dose of Levo should be 24 hours before the test.

A B Complex containing Biotin, or Biotin supplement, should be stopped 7 days before the test.

Anything else take after the blood draw on the day not before.

[Mum23girls in reply to SeasideSusie]

Thankyou

[SlowDragon Administrator]

Headaches are a hypothyroid symptom

Propranolol will slow down uptake and conversion of levothyroxine. It’s typically used to treat hyperthyroidism

However you MUST NOT stop propranolol suddenly. It has to be weened off incredibly slowly.

How much propranolol are you taking?

How long at this dose

Propranolol also tends to lower magnesium and may lower parathyroid hormones

See “Common Questions”

“ Is there anything else I should know”

Drugs that may decrease PTH include cimetidine and propranolol.

labtestsonline.org.uk/tests...

Essential to test vitamin D, folate, B12 and ferritin

[Mum23girls in reply to SlowDragon]

Thankyou. I’ve been taking propanalol 80mg and noritryptiline 20mg for about 3 years for migraines. Just been on levothyroxine 50mg for a year now.

[SlowDragon Administrator in reply to Mum23girls]

50mcg levothyroxine is only a starter dose of levothyroxine

Dose should be increased as fast as tolerated

Bloods should be retested 6-8 weeks after each dose increase

The aim of Levothyroxine is to increase the dose slowly in 25mcg steps upwards until TSH is under 2 (many patients need TSH significantly under one) and most important is that FT4 is in top third of range and FT3 at least half way through range

NHS guidelines on Levothyroxine including that most patients eventually need somewhere between 100mcg and 200mcg Levothyroxine.

nhs.uk/medicines/levothyrox...

For full Thyroid evaluation you need TSH, FT4 and FT3 plus both TPO and TG thyroid antibodies tested. Also EXTREMELY important to test vitamin D, folate, ferritin and B12

Low vitamin levels are extremely common, especially if you have autoimmune thyroid disease (Hashimoto's) diagnosed by raised Thyroid antibodies

Ask GP to test vitamin levels and thyroid antibodies

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

Private tests are available as NHS currently rarely tests Ft3 or thyroid antibodies or all relevant vitamins

List of private testing options

thyroiduk.org/getting-a-dia...

Medichecks Thyroid plus ultra vitamin (doesn’t include folate)

medichecks.com/products/thy...

Thyroid plus vitamins including folate (private blood draw required)

medichecks.com/products/thy...

Medichecks often have special offers, if order on Thursdays

Thriva Thyroid plus vitamins

thriva.co/tests/thyroid-test

Blue Horizon Thyroid Premium Gold includes vitamins

bluehorizonbloodtests.co.uk...

All four vitamins need to be regularly tested and frequently need supplementing to maintain optimal levels

Even if we often don’t start on full replacement dose, most people need to increase dose slowly upwards in 25mcg steps (retesting 6-8 weeks after each increase) until on full replacement dose

NICE guidelines on full replacement dose

nice.org.uk/guidance/ng145/...

1.3.6

Consider starting levothyroxine at a dosage of 1.6 micrograms per kilogram of body weight per day (rounded to the nearest 25 micrograms) for adults under 65 with primary hypothyroidism and no history of cardiovascular disease.

gp-update.co.uk/Latest-Upda...

Traditionally we have tended to start patients on a low dose of levothyroxine and titrate it up over a period of months.

RCT evidence suggests that for the majority of patients this is not necessary and may waste resources.

For patients aged >60y or with ischaemic heart disease, start levothyroxine at 25–50μg daily and titrate up every 3 to 6 weeks as tolerated.

For ALL other patients start at full replacement dose. For most this will equate to 1.6 μg/kg/day (approximately 100μg for a 60kg woman and 125μg for a 75kg man).

If you are starting treatment for subclinical hypothyroidism, this article advises starting at a dose close to the full treatment dose on the basis that it is difficult to assess symptom response unless a therapeutic dose has been trialled.

A small Dutch double-blind cross-over study (ArchIntMed 2010;170:1996) demonstrated that night time rather than morning dosing improved TSH suppression and free T4 measurements, but made no difference to subjective wellbeing. It is reasonable to take levothyroxine at night rather than in the morning, especially for individuals who do not eat late at night.

BMJ also clear on dose required

bmj.com/content/368/bmj.m41

bestpractice.bmj.com/topics...

[SlowDragon Administrator in reply to Mum23girls]

Is this slow release propranolol ?

Or several smaller doses per day?

Discuss with GP reducing propranolol down .....very very slowly.

[Mum23girls in reply to SlowDragon]

Thankyou. This is all very helpful. Will have a good read through. Really appreciate your expertise.

[SlowDragon Administrator in reply to Mum23girls]

pubmed.ncbi.nlm.nih.gov/168...

I was stuck on propranolol for almost 20 years

Even on only 40mg per day that had significant affect on levothyroxine.

[TaraJR]

My surgery has said I must not take Vitamin D supplement if I'm having a Vit D test. I've been supplementing all through lockdown, so I've stopped now ready for the bloods in 2 weeks.