Q: What Tests can be Used to Rule Out Physical Causes of Moods?
I was recently diagnosed with bipolar disorder and I do believe the diagnosis is
correct, but my doctor ran some blood tests to rule out physical causes of
my moods. I forgot to ask what he was looking for. What do doctors
generally look for with "oh you have mood symptoms" blood tests. Several
websites/books tell us that doctors do this to rule out other illnesses
that can cause depression, but I'm not sure what they are. I'm thinking thyroid
function, but is there anything else? I know the right blood tests can probably
tell doctors a fair amount of information about a person's health, but is that
really all that was needed? I'm curious because I've never seen a
full explanation of what I've only read as "physical illnesses that can cause
bipolar (or just depression) like symptoms" means although I think I
recall reading "thyroid disorders and other", but what is other? I'd never
be able to enter the medical profession, but I like reading about
this kind of stuff. It's fun.
PS. I fear the list might be a bit long.
Dear Kathryn --
Good question. The list of standard things to test for is actually very short.
It includes thyroid. After that, there is a question of how many haystacks to
turn over, looking for a needle. For example, sometimes people have
bipolar-like symptoms after a stroke, or a head injury. But we don't routinely
do a brain CT scan, or an MRI, every time someone presents with bipolar
symptoms. Unless they are over 40 or so. A new-onset bipolar disorder, over
age 40, is actually pretty unusual and might in some cases be worth a search for
some underlying basis of the late onset.
Again, in general, the only standard, widely accepted blood test,
diagnostically, is thyroid. The idea, of course, is to make sure that what looks
like bipolar disorder is not hypothyroidism (or in some cases, particularly if
someone shows up looking manic, but not exactly manic, hyperthyroidism).
However, there are other reasons to get a blood test at a first visit. Most of
the treatments we might consider have the potential to cause dangerous
physiologic changes, so we need to know, before treatment starts, exactly where
we are starting from. For example, lithium can interfere with kidney function,
so it is routine to check kidney function at some point. But since lithium
treatment requires numerous blood tests, I think it is within standard of care
to delay the first blood tests until after a trial of low-does lithium, as long
as the person is young and physically healthy as far as she/he knows. But some
doctors would get a "baseline" for kidney function before starting with him in
Likewise, the whole family of "atypical antipsychotics", which we use as mood
stabilizers, (sometimes in very low doses) can cause increases in blood glucose,
progressing even to diabetes. They can also cause increases in cholesterol. So
we need to know where glucose and cholesterol levels are before we start, or
very near starting (some of those changes can take a while, but some of them can
In general, I try to limit laboratory testing: it can be expensive, it can turn
up unanticipated abnormal values that are sometimes just a statistical fluke,
and some involve at least scheduling hardship if not physical discomfort for my
patients. So I'm a little less likely to order "baseline" labs until I know
what I'm going to use them for, compared to some of my colleagues, I think. But
other doctors, particularly in busy clinics were they can't think through the
details every time, might order a whole panel of baseline tests for everyone.
That is not outside standard of care either.
Finally, there are other needles (in haystacks) out there that a few doctors
might think are worth checking at the outset: vitamin D, B12, calcium, (all of
these are blood tests). That is not an official list. Oh, and some doctors
might even want a urine sample, and in which to look for marijuana and other
substances of abuse. I think talking to patients is a better way to get that
information, but I will miss substance use problems in some people here and
there (on the other hand, it does not subject people to the indignity of a urine
drug screen either; a trade-off).
Thanks for your question.
Published October, 2009