Fasting before home test.

[Horsecrazylady79]

HI, this is a question for my mum. I've finally managed to persuade her to do a private test to get a full view as her TSH has been consistently over 2 and she has a whole host of hypo symptoms, and has for many years. She has recently been diagnosed with Systemic Sclerosis which is also causing overlapping symptoms.

 6 years ago she had to have Nissan fundalplication as the sphincter in her stomach had stopped working. There have been complications lately that mean she is once again under the gastroenterology consultant as the only thing she can tolerate is cappuccino.

 I know that it's best to fast before the test, however she wakes up every morning at 4.30am and has to have a cup of her cappuccino to relieve her thirst. Will this be OK if she still takes the test at 9am? I know she wouldnt cope going a full 12hrs without a cup as she is unable to tolerate water whether it be cold or warmed.

Thank you

[SeasideSusie Remembering]

Can she not have juice to quench her thirst rather than a caffeinated drink? Coffee can interfere with results

healthline.com/health/fasti...

Even if you drink it black, coffee can interfere with blood test results. That’s because it contains caffeine and soluble plant matter, which might skew your test results.

pubmed.ncbi.nlm.nih.gov/610....

Caffeine lowered serum TSH and GH in a dose-dependent manner with ED50 values of 30 and approximately 50 mg/kg, respectively. TSH levels were depressed 1 to 6 hr after injection and correlated with serum caffeine levels greater than 20 micrograms/ml. The decrease in serum TSH was followed by decreases in serum 3,3',5-triiodothyroxine and thyroxine 4 hr after caffeine administration.

[Horsecrazylady79 in reply to SeasideSusie]

Unfortunately she cant, no. She can literally only tolerate the cappuccinos that she has, over the last few months she has been under the dietician who has tried many different things as she understandably is losing weight.

[SeasideSusie Remembering in reply to Horsecrazylady79]

Well the coffee may affect the results.

[Horsecrazylady79 in reply to SeasideSusie]

When do you think she should fast from?

[SeasideSusie Remembering in reply to Horsecrazylady79]

Food-wise she can eat as normal the day before, just don't eat before the test on the day, and of course we advise water only before the test, this is to ensure that no food or drink can affect the results. Not all food and drink will affect the results but this way nothing can.

[jimh111]

There is no evidence that fasting affects thyroid function tests. One sloppy study claimed to show an effect but this was followed by a second study by the same team that corrected their error (without an apology for causing confusion).

Normal amounts of coffee, two or three cups a day makes no difference to TSH. Note that coffee (and bran) reduces absorption of levothyroxine. So, don't have coffee around the same time as levothyroxine.

There is no need to fast or avoid coffee before a thyroid blood test.

[mountainice in reply to jimh111]

That good. I've always waited and had no early cup of tea!