Fasting bloods help

[Anzay15]

Hey so I have a blood test today at 11.30.I know you're not supposed to eat or take levo before bloods. My issue is my blood pressure tends to drop during blood tests and I feel and can faint.

If I take my levo after my test, I still can't eat until 12.30 or more depending on when the test is done and. I dont think I'm going to be OK until then.

What do I do in this situation? I haven't eaten anything yet or taken my meds

[SlowDragon Administrator]

If you feel faint eat now

If you can manage to wait…eat immediate after blood test

Then take levothyroxine 1-2 hours later

[Anzay15 in reply to SlowDragon]

Thank you, I ended up eating as I know I feel poorly after my blood test if I don't.

Also, is the dose directly linked to your weight? Or can you be on a lower dose?

[SlowDragon Administrator in reply to Anzay15]

Some people need lower dose, some need higher dose

Guidelines on dose by weight can be helpful if your GP is reluctant to increase dose …….but you think you need higher dose levothyroxine than currently on

[Anzay15 in reply to SlowDragon]

No I don't want to change my dose. My doctor told me to reduce it to 100mcg based on my results last time. They did a blood test yesterday to see how I'm getting on with the 100mcg. I've been taking my normal 125mcg as I feel fine and I told my doctor I haven't reduced it.So based on yesterday's result which won't be entirely accurate since I ended up eating, they're going to see if I need 100 or 125. Based on my weight, it should be 125.

Not once have the doctors mentioned the weight thing. My ferrin, b12 and vitamin d weren't optimal last time either, which weren't mentioned by the doctor obviously

[Manycrafts]

I take 100mcg Levothyroxine and also Bisoprolol which also lowers BP and one or both can make me feel dizzy for a while an hour or so later. I have always drunk a large glass of water with my tablets, but now I have another glass half an hour after taking them. This increases your blood volume and so also raises your BP which may help you as well.

I find the instructions about what you can eat and when can differ, but the important thing for the test is to only have water the 4 hours beforehand. I doubt eating sooner afterwards on just the days of your test would have much impact or harm. My prescription says different to what a pharmacist told me, but it seems the main things to avoid for 4 hours afterwards are foods and drinks with the metallic substances calcium, iron and magnesium. So many things seem to affect Levothyroxine absorption like fibre and even HRT and how are we supposed to know by how much they affect things, so which to avoid the longest?

As for weight I've never heard my doctor mention it in connection with my thyroid dose, but during lockdown when I lost over 2 stones in weight, my dose was reduced after a routine annual test by the Thyroid Register. A clue I hadn't connected at the time was a couple of my toenails becoming more brittle and growing out much thickened. A year later I had to see an endocrinologist about another matter and she commented on my thyroid dose being unusual to have been reduced. When I told her how much weight I had lost she said that would have been enough to need a reduction in my dose. No-one tells you these things, but now I know when to ask for a test if I manage to lose as much weight again. My toenails eventually grew back normal, but all the nurse did at the time was test for fungus, no suggestion of it being thyroid levels or suggesting a test.