Anyone know what to do before a blood sugar test???

Hi, sorry this is completely unrelated to thyroid problems, but I thought you gifted ladies and gents would be most likely to know about blood sugar testing. I'm due to have mine tested on Monday morning. Does anyone know if I am best to eat beforehand, not eat, have a big bun with extra icing, stay well away from anything with even the vaguest hint of sugar......?

Seriously, what is the best thing to do before the test to ensure it gives a clear picture of whether I'm having blood sugar problems or not? I am a complete ignoramus here - any diabetics or pre-diabetics know what to do for best?

24 Replies

  • I think it depends on the type of blood sugar test you are having. Do you know the specific name? Is it a single test or several over the course of a few hours? I suggest you phone whoever is doing the test tomorrow to find out more information so that the results of the test - and your precious blood! - are not wasted. :)

  • Argg! Thanks, Sandi. I didn't know there were different types! I know it's just one test, on the spot, I assume with one of those little meter things. I know most surgeries own them.

  • Chancery, ring the surgery and ask whether it is a fasting or non-fasting test.

  • Thanks, Clutter. I'll catch them in the morning, but I'm not sure if they'll know and the phlebotomist doesn't come in every day, so I may be stymied if the receptionists don't know!

  • Chancery, just treat it as if it is a fasting test.

  • Yeah, I was just thinking that, Clutter. I'll phone tomorrow but if they don't know, it sounds like fasting would be best.

  • Check with the surgery but 9 times out of 10 it's a fasting test. My doctors does all fasting blood pulls as first-thing morning appointments because they like you starved and grumpy after no food for at least 8 hours. For this reason they play safe and say no food after 8pm the previous evening.....early supper is a must!

    No snacks, sweets, fruit etc..

    No tea or coffee, especially in the morning (by force of habit!)

    Water is fine, in fact the phlebos like you well hydrated to get a good vein show, so keep water handy throughout evening and night and have a good glassfull before the draw. Taking my thyroid meds as normal was OK too.

    On the other hand...there is the A1C test which measures your blood glucose levels over the previous 3 months (it's all clever stuff!) and that one you do Not need to be fasted.

    So I guess it all leads back to finding out from your doctor's surgery what test you are having *sigh*. good luck!

  • Thanks, Spongecat. I'm afraid I've already queered not eating after 8PM - I had my supper at 9.30! But I'll leave it at that now and skip breakfast in the morning. Oh, what am I SAYING? Just realised I'm having this done Monday, not tomorrow! I swear my brain is going down the toilet.

    Thank you, I now know not to eat after 8pm on SUNDAY! That's assuming I am bright enough to actually make it to the doctor's....

  • I assume you mean a FULL Blood Glucose tolerance test ?

    I believe you should fast for 12 hours prior but certainly a big sticky bun would be rather stupid

  • No idea, fedup. I just asked if I could have my blood sugar tested and the doc said 'fine, no problem', so I have no idea what they actually do. As for the sticky bun, I kind of thought it had a logic to it - if my body can't cope with sugar I thought that might show up after a big, sticky bun, but maybe my logic and the way the body actually works are two different things!

  • How's the T4 going Chancery - have you had an increase ? Pancreas - just another link in the Endocrine system that may need more thyroid hormone. Read recently about the adrenals and the pancreas and how they may be looking at the wrong thing with diabetes - can I remember where I read it ? - so wish I could. Have googled so many variations - nothing :-)

  • Hi Marz. Levo's not going great, in that it's made no changes to anything, except I am getting way more migraines than before I started taking them, plus I'm having more trouble with my appetite and weight gain. I thought they were supposed to help that! So no, no luck so far. To be truthful, if my blood tests have dropped back to normal again when I am retested I am going to stop taking them, since all they have done is added to my list of problems. That's probably the worst science since science began, but I am currently worn out with drug side effects. SO very, very tired of it.

  • ..maybe the T4 doesn't mix well with the pain relief meds :-)

  • Oh, I know - it's the most likely culprit, no discussion. Whenever there is trouble with a medicine, you can bet your boots Carbamazepine has had a hand in it...

  • If its just blood drawn at your GP surgery it will likely give a false result if your hypothyroid but if they do a full Glucose tolerance test at the Hospital it should be totally OK

    Been thru that years ago with my husband

    LFTS can be dodgy when hypothyroid is not treated

  • Ah, fed up, well I'll be stuck then! Once my doc gets an all-normal reading, the problem is over!

    But you say LFTS can be dodgy. Liver function tests? And why does being hypothyroid affect blood sugar tests? Can I ask also what happened with your husband? Sorry for all the questions - all this is new to me so I haven't a clue what's going on!

  • The thyroid is the conductor of the entire endocrine orchestra of the body

    theres 40 hormones in the brain alone never mind every other part of the body hence when the Conductor is crook so are all the musicians in the orchestra

    So often the pancreas and the liver throw wobblies

    The big problem is GPs look at RANGES instead of recognising that its where results are in those ranges across everything that matters

    It seems that in Doctors entire time in Med school they only spend 10 minutes on the thyroid despite its effect on the entire body

  • Ah, fed up, it's probably only ten minutes on their good days, when they are concentrating hard!

  • I had one on Monday and I had to fast for 12 hours but drink lots of water x

  • Thanks, Tjpink - that's what I'm going to do.

  • They like to test your blood sugar levels 12 hours after you have eaten, which makes no sense at all. If you have blood sugar levels over about 7 despite not having eaten, then they can classify you as diabetic. However i just had three tests which came back , one at 6.9, one at 10 and the other over 7 but cant remember the no. One doc said i was fine, the other in the same practice says i am diabetic.

    I have seen my bs tests and it looks like they have been high for the past 8 years or so, which is when i got fat round the middle.

    The 10 reading was when i had some rice the day before. Even wholegrain rice pushes up my blood sugar levels for two days. :-(

    Sugar only pushes it up for a short time and then i drop low. ( to about 5)...

    Good luck, i am still trying to make sense of it all

    G xx

  • Thank you for all that info, Galathea. I had only just started to realise I'd have to go find out what was normal and what wasn't, because I'd have no idea what the figures meant, cause I think they just tell you on the spot, don't they? Now at least I've got a reference point! As for the fat round the middle - had that for a goooooood long while...

  • Hi, I'm a phlebotomist/Hca, you need to fast for minimum of 10 hours, this applys to glucose tolerance test too, but you have to have a raised fasting glucose before the glucose tolerance test... Hba1c is generally done every 6 months if diabetic or a BMI over 30 not diabetic, if diabetes is suspected they do fasting glucose and hba1c together.... Well at my surgery we do... Hope this helps... Drink plenty of water😀. Jb

  • Thanks, Julie, great to get it from the horse's mouth; 10 hrs it is. Can you tell me what test the phlebotomist is likely to do? I asked to have my blood sugar tested and the doc said fine, but he didn't specify what they are likely to do. I'm assuming it will just be a finger prick test with the little meter - is that right? He isn't testing for diabetes or anything, just giving me what I asked for! What's the most likely routine thing she'll do?

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