Why would my doctor put these on my blood test … is he only checking the function of my thyroid?

He told me I needed blood work for something. That something is one the lab order, but I noticed after I left that there were other things requested, too. The lab order includes creatinine, T4, and TSH.

I tried looking on the web, but I couldn’t completely answer my own question. From what I can tell, T4 is thyroxine and TSH is thyroid stimulating hormone, and both relate to thyroid function. But what about the creatinine? I read that it’s related to the breakdown of creatine in the muscles. I read that it’s used to assess kidney function. I don’t see how that relates to me, though. Any ideas?

I’m going to ask my doctor eventually, but my next appointment isn’t until the end of June and even then I won’t be seeing the same doctor. I suppose I could ask the person taking my blood when I get that done next week. Until then, any knowledge will be appreciated.
My doctor is a psychiatrist, so the appointment was to get new prescriptions. I take Lithium and the blood work was to check my Lithium levels. In case it matters, I take Trazodone, too, to help me sleep. I guess I’m overweight, too, so is that what the thyroid inquiries are for?


  • some thyroid conditions can cause mood disorders, so that was probably the purpose of that test. Lithium is cleared through the kidneys, so the creatinine test would check kidney function for this reason.

  • Matthew N

    The T4 and TSH tests are part of the "Thyroid Function Panel," and are appropriate if checking your thyroid. The creatinine is usually used to ballpark your kidney function. Not knowing more about why you’re getting worked up at the doctor makes it hard to say why it was ordered, but it’s a standard test often included in a "Chem 7" (7 different chemistry tests of your blood) which addresses many of your body’s functions.

  • cloe s

    Some Thyroid conditions can bring on mood changes

  • Hyperthyroidism melts muscles. Serum creatinine may increase in those who lose a lot of weight in hyperthyroidism.
    However the test is not required for diagnosing or treating thyroid condition..

  • drdave1666

    one of the problems with lithium is potential kidney damage…he asked for the creatinine as a screening test for kidney function

  • W W D

    Thyroid abnormalities and mood disorders are often confused for each other. It’s routine to check thyroid function in people with psychiatric illnesses.
    Lithium has a very small therapeutic index; that is, the difference between the amount needed for it to work properly and the amount that causes "overdose" problems is very small. Lithium, if you look on a periodic table of the elements, is closely related to sodium. It’s important that your renal function not offer any surprises, as a lithium overdose, however inadvertent, could be most unpleasant, and perhaps even require hemodialysis (artificial kidney machine) to treat.
    There’s really not much going on here. The doctor is just being normally cautious, and the details are really so boring that he just didn’t want to bother you with them.

  • Ashton T

    WhatWould, It’s good to make sure you understand the approach your physician is taking to handle your case. The days of leaving it all in the hands of the doctor, trusting blindly and asking no questions are gone. You however, seem to in a state of unrest, stress even, over your doctor’s management of your case. The last thing you want to do is go ask a bunch of people what your doctor is doing or thinking. That goes double for the people that draw the blood in the lab. They are a surley bunch of needle pokers and are not to be trusted (kidding). I have worked in the clinical field most of my adult life. It is because of this I have the opinions I do. I can tell you from personal experience that most problems that develop between patients and their doctors come from the patient doing exactly what you are doing. Not the research part (a bit premature but not harmful) the third party inquiries. Immagine your doctor posting the question on YA, "Does My Patient Not Trust Me?"

    Now what is the correct approach? Make sure you have all your questions answered before you leave the doctors office. If you get home and decide you’ve got another question, call the doctor’s office. The doctor will call you back or assign a nurse to do so with the information. You can and should use the resources of the Internet to learn about your case but not necessarily the workup. At this point they are still screening you for so many potential ailments they can’t handle you, "so what do you think?, so what do you think?, huh?, huh?, huh? -ing them every ten seconds. In the end, if you trust your doctor cut him a little slack, if you don’t trust him go find another.

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