Hello this is my first post here so I apologise if I do anything wrong. I am currently 10 weeks pregnant and on 50mg levothyroxine 5x a week and 75mg 2 times a week.
I was prescribed this for subclinical hypothyroidism by my IVF clinic.
Now I'm 10 weeks pregnant and with the NHS. I didn't realise that biotin could mess up thyroid function tests and did not stop my pregnancy supplement before my blood test at my booking appointment.
When I rang the midwife to ask to redo the test she said she will not test me again for another 18 weeks as my levels are in the normal range and everyone else takes multivitamins before the tests so it's fine.
If the test results I have are valid then I am indeed well within in the normal range and wouldn't be causing a fuss, but my understanding was that the biotin made the results invalid?
Also I feel like the results might indicate that I might need to decrease my dose a bit since the tsh level has dropped from 4.8 to 0.8 in a month and the free T4 levels are relatively high at 16.4 which seems to be out of the first trimester reference ranges I see online. But I'm not a doctor or a nurse and I don't want to mess about with medication off my own bat.
I am anxious right now as I've had 2 prior miscarriages in the first trimester and I suspect they were due to undiagnosed thyroid issues since I had many of the symptoms.
What would you do?
Written by
Lovetoread88
To view profiles and participate in discussions please or .
Others have far better and deeper understanding of the pregnancy. issues than me.
An 18 week gap, in pregnancy, is quite simply ridiculous.
You need the reference ranges from the lab that did your test. They vary from lab to lab and what looks fine using ranges you can easily find, would look bad against another set.
If necessary, call the lab and ask them what their ranges are. But you might find them online.
helvella - Biotin supplementation and testing
A short article about how and why biotin can affect blood tests. Includes information about how to avoid any problems and how much biotin some foods contain.
Thank you this is very reassuring. The supplement had 150micrograms so it sounds like it may not have had a large impact. I have the reference ranges that the hospital gave me. I was comparing them to the advice I saw from other nhs trusts which alter their range for pregnancy and by trimester. Although I still think their approaches seem better than my local trust, it's good to know that the reference ranges don't transfer across from NHS trust to trust as it means my googling is not relevant
It's good to know that the midwife's approach isn't totally off base (other than the massive gap between appointments which is my trust's policy). So I might be ok just getting some extra testing done privately to monitor but I don't need to redo this one
18 weeks is a long time to leave between tests when you're pregnant! So much can change in that time. I think that is bordering on negligence, but I don't know what you can do about it. Can you get private testing?
Also I feel like the results might indicate that I might need to decrease my dose a bit since the tsh level has dropped from 4.8 to 0.8 in a month and the free T4 levels are relatively high at 16.4 which seems to be out of the first trimester reference ranges I see online.
You should never, ever dose by the TSH. It is irrelevant. And when you're pregnant you need high T4 because the baby takes a lot of it. What is the lab range for your FT4 test? Ranges you see on-line have nothing to do with your results because they vary from lab to lab, and we need the range that came with your result.
My trust's policy is to test by trimester and I've happened to end up getting my 1st appointment quite early and my 2nd appointment looks to be right at the end of the 2nd trimester. I agree with you and some of the other posters that I likely need more testing and maybe I can get it via the early pregnancy unit. I've asked for a referral and will also be getting a private test in the meantime.
The results with reference ranges are:
Free T4 16.4 pmol. Reference range 10.8-25.5pmol.
TSH 0.82 m IU/L
Reference range: 0.27-4.2 MIU/L
So if high T4 is good then both look pretty ideal currently.
Hello, thank you for explaining. What does the percentage refer to in your post and how do you know the free T4 is a low level despite being within the written range?
I'm posting the bit below in the hope that it explains more about ranges.
This is a link to a very good article in the British Medical Journal discussing what the 'normal range' really is. Very readable.
The normal range: it is not normal and it is not a range
This blog has the abstract of this paper plus link to the original full paper. Also includes some extra links to a video and some other related information.
Because ranges vary, we cannot compare a result of, say 2.5 from one laboratory and a result that might be the same, lower, or higher, from another laboratory.
The best we can do is work out how far between the bottom and top of the range the result lies. And that is expressed as a percentage. Very imperfect but all we have. It would be much easier if all labs had the same ranges.
But a side benefit is that the percentage can give a feel for where the result lies.
In order to do that, we have a couple of calculators.
I'm sorry, I didn't explain very well. The percentage is through the range. In someone who doesn't have any thyroid problems, the FT4 is usually about 50% through the range, but hypos usually need it higher. So, as you are hypo, your FT4 is low - and by the same token, you are hypo because your FT4 is low.
The ranges are just a rough guide, telling you what the general population results are. But when they test the general population to get the ranges, they obviously include a lot of people with undiagnosed thyroid problems. The majority of these people have an FT4 of around 50% so we take that as being 'euthyroid' (normal). But it is only a rough guide. And we all have our own, personal set points which, unfortunately, are never tested when we are well. So we don't know what they are. That said, it would be unusual to find someone with an FT4 that low who is 100% healthy. So, don't be taken in by the 'your results are all in-range' from doctors. It's not about being just anywhere within the range, it's about being in the right place. And, when you are pregnant, your baby is going to be taking a lot of you T4 until s/he develops her own thyroid. So , it needs to be over 50% through the range.
And if all that sounds a bit garbled, read helvella's link and I'm sure you'll understand better.
Has dose levothyroxine been increased as soon as conception was confirmed
Has GP tested vitamin D, folate, B12 and ferritin
Please add results if you have them
Low iron/ferritin can be cause of miscarriage
Suggest you get FULL thyroid and vitamin testing done yourself NOW
Recommended that all thyroid blood tests early morning, ideally just before 9am, only drink water between waking and test and last dose levothyroxine 24 hours before test
This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip)
Private tests are available as NHS currently rarely tests Ft3 or all relevant vitamins
If you normally take levothyroxine at bedtime/in night ...adjust timings as follows prior to blood test
If testing Monday morning, delay Saturday evening dose levothyroxine until Sunday morning. Delay Sunday evening dose levothyroxine until after blood test on Monday morning. Take Monday evening dose levothyroxine as per normal
No vitamin levels have been tested by the GP, I will get this done through some of the self testing services thank you.My thyroid issues were picked up by my IVF clinic. They're subclinical although I have only ever had my TSH level tested. I have had ongoing unclear autoimmune issues for many years e..g hives, fatigue and have never seen such a difference as I have since starting levo so I'm hoping to stay on it.
The lab ranges for TSH during each trimester of pregnancy are different. Make sure you are comparing your results to the TSH ranges for pregnancy. A lower TSH during pregnancy, especially the first trimester is acceptable. With the ft4 level you are not over medicated. You should have labs every 4 weeks when pregnant. I am pregnant. This is how it’s done.
Depends on the NHS trust sadly, some are once a month, some a once a trimester. It still wouldn't make sense anyway though as with once a trimester you'd think it would be 12 weeks between tests not 18. Could be the way my appointments have worked out or could be a miscommunication. I'm going to get my GP to refer me to the EPU anyway to ask for monthly testing
Also ask your GP to refer you to the recurrent miscarriage clinic as you have had two previous, that way they will keep an extra eye on you and may even do more scans.
Oh and congratulations! I’m sure all will go well!
Won't your IVF Clinic do any blood tests for you? I did IVF and I was called in for blood tests quite a few times when I got pregnant. (Sadly I didn't stay pregnant for very long.)
But my IVF treatment was a long time ago, and perhaps methods have changed since then. Although I suspect it is money-saving stinginess that has reduced blood testing in both IVF, and in pregnancies being dealt with by the NHS.
My IVF clinic were amazing and were doing regular blood tests for me (I paid per test so no reason for them to be stingy) but they are only licensed to treat people until 7 weeks of pregnancy.I've got my GP appointment booked and my medichecks test sent off now so should be all good.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
test interpretation help please 
Blood test results advice
Monitor my health test results
