Introduction to lab values and normal ranges | Health & Medicine | Khan Academy

Introduction to lab values and normal ranges | Health & Medicine | Khan Academy

So I have a slip of paper. Let’s go through
these lab values. I actually put down
a number of values down that we’re going to pretend
for a moment are my labs. And you can see the range,
and the units next to them. So let’s go through
it piece by piece. And actually, while
I do it, I’m actually going to show you some
shorthand techniques, so that you can
understand, if you ever see this in the future,
what it refers to. So this is some shorthand
that people have come up with. This isn’t necessarily
something I’ve come up with. I learned it from
folks ahead of me. But it’s been used
not just in the US, but most parts of the world. It’s pretty uniform. So if you’re looking
at these labs, here’s a quick way
to transcribe them. So imagine that you
have to quickly put it on a piece of paper and move on. This is how you would do it. So you would draw a little
stick diagram like that. And in the far left,
you’d put the number 5. And this refers to the first
row, the White Blood Cell row. And we know that
the value is 5,000, so that’s what the 5 represents. And it’s understood
that that number is in thousands of
cells per milliliter. So if you see a 5, you know
we’re talking about thousands of cells per milliliter. And the next question is, well,
what are those types of cells, if you actually were
to look at them? We know they’re
white blood cells. But exactly what type they are
is actually in the six rows beneath. So these six rows tell you
the breakdown of this number. So that’s why they’re percents. And so the 5,000
cells break down into segmented neutrophils. I’m going to write
that as an S with a 61. And bands, there are 3% bands. Lymphocytes are 29%. And then we have monocytes
at 4%, basophils at 1%, and eosinophils at 2%. So these percentages for the
different types of white blood cells are going to
add up to 100, right? So let’s just double-check. We’ve got 7 and 29
is 36, and 3 is 39. Yep, 100%. So that’s how you quickly
can see the different types of white blood cells that are
floating around in your body. That’s what those
numbers represent. So then the next two numbers,
hemoglobin and hematocrit, go in the top and bottom
of this stick diagram. And again, whenever you see
these numbers like this, I could look at
that and immediately figure out that that’s the
red blood cell content. Those two numbers both
reflect red blood cell content in the blood. And then the last
cell on this side represents the platelet count. And 227 represents 227,000
cells per microliter. So before, we were talking about
milliliters for the white blood cells. But now, for the
platelets, we’re talking about microliters. And in fact, I’ll put
“cells” in quotes, because we know it’s
not really cells. These are little cell fragments
that are the platelets. So that 227,000 tells you
about how many platelet cell fragments are floating around
in one microliter of blood. So that’s the first
chunk of data. So that’s all this information,
summarized very quickly in that stick diagram. Now let’s move on
to the chemistries. And so if someone orders
a Chem 7, then that would be the first
seven of these. And if they order a Chem 10,
then that would be all 10 of these. So this is how you would draw
this out as a stick diagram. It kind of goes like this. And the Chem 10, the
last three, go in here. So the sodium goes
in the top left. And below that is the
4.3 for potassium. And just going systematically
all the way through it, so for chloride, it’s 103. Bicarbonate goes as
22 right below that. And then the creatinine
goes in this cell, 0.8. And then the blood
urea nitrogen– sometimes they call
that the B-U-N, that’s just the first letter
of these three– is 15. And then the fasting
glucose is 92. And then the calcium
goes in the top of this little
wishbone-shaped stick diagram. That goes right there. The magnesium goes on this side. And the phosphate
goes on this side. So that’s the Chem 7 on top. And the Chem 10 would
be all of that together. And then, at the bottom,
we have some liver enzymes. And also, there’s a stick
diagram for that, as well, kind of a fast way to draw it. And it’s basically just an x. So the top of the
x is two numbers. So you usually write the total
bilirubin like this, 1.1. And then you put a slash. And then you put the
other number there, the direct bilirubin, 0.1. And then on the left,
you put the AST. And on the right,
you put the ALT. And at the bottom, you put
the alkaline phosphatase, 76. So this is how the
numbers break down. And so, again, if you ever see
any of these stick diagrams and you’re wondering
what they refer to, now you have broken the code. You know what number goes where. So if you see, for
example, this number at 22, you immediately know that
they’re talking about the ALT. So this is the way that
people quickly diagram things. And now I know, when
people look at labs, the first thing they
want to know is, hey, is this good or bad? And so, they want to
look at these values, and they want to compare
them to the ranges. They want to say, hey, does
this fit into the normal range that people expect? So let’s talk about that. Let’s talk about normal
range and what normal means exactly, because I know
that’s the first thing most people will want to look at. So let me draw out what a
normal curve would look like. So if you actually, let’s
say, took everybody, let’s say 10,000–
it’s not everybody, but let’s say a big chunk
of people– 10,000 people and asked them all to tell you
their white blood cell count. They will give you, of course,
many different numbers. Probably wondering what you’re
doing with that information. But let’s say they
give you their answer. And let’s say you plot
it all on a curve, and you draw a little diagram. This would be basically
what you would find. You’d say, OK, most people
have a white blood cell– and this is white
blood cell count. Actually, sorry. This is white blood
cell count down here. And this is, of
course, in thousands. We said thousands
per milliliter, thousands of cells
per milliliter. And this is frequency. This is the number of people. I’ll just write f for frequency. So you would say,
OK, while there are a lot of people in
this range right here– and in fact, 95% of people
fall in to this middle section in this area. So this is definitely
the bulk of people that fit between 4.5 and 10. And that’s actually how most of
these ranges are decided upon. They say, OK, where do
the bulk of folks lie? And it’s usually between those
numbers that are in the range. And that also means, if you
think about it, that there is, of course, somebody out here
and somebody up here, right? I mean, that is, by
definition, going to happen. You’re going to have
5% of people in one of those two tails combined. So whenever you
see a range, just keep in mind that there is
some normal variance, they’re called, that kind of go
above or below that range. But that range usually
captures the majority of folks. So when thinking
about that, when thinking about what exactly
goes into a normal range, consider some of the things
that could make what is normal differ. So for example, let’s say I
check someone’s hematocrit. Let’s say I’m looking
at the hematocrit, and I want to find out
if it’s normal or not. If I look at a baby’s
hematocrit, but I use, let’s say, an adult
range, then it would be very, very
unusually high. So a newborn baby has
a very high hematocrit, so I really should be comparing
it to other newborn babies. So age is really
important to consider. So you want to make sure
that the range of values is age-appropriate. You also need to make sure
that gender is considered. So for example, the normal
range for men’s hematocrit is a little bit higher
than the normal range for women’s hematocrit. So range matters for
age and also for gender. Now, different labs
will also differ. So it’s actually
quite interesting. You can even go online and
see what the normal range is for a lot of these
things I have here. And the numbers will be
a little bit different from what I’ve shown you. So if you go from
one lab to another, you’ll get different numbers. And in fact, lab
technique also matters. So even within a lab,
depending on the technique that they use to get
an answer to something, the range could differ. And that actually
matters, particularly for things like this. So these IUs that
I put down here, they stand for units,
or international units. And that’s specific to a certain
type of lab assay that’s done. And again, that depends on
the exact assay that’s done. And that’s going to
change the range of values that you get there. So consider the technique. And finally, consider
this situation. So if you have, let’s
say, a person who is supposed to come in
for a fasting glucose. And usually, you’re told, just
don’t eat anything overnight. And don’t have breakfast. And come in and get your
blood taken first thing in the morning. That’s a pretty common scenario. Then you would have a
normal fasting glucose. And it should be below 100. But let’s say, by
accident, you decide to have a little
snack in the morning, because that’s your usual thing. You have some toast. Your blood glucose
could go up as a result. So that glucose
result could be OK, if someone knows that
you didn’t fast, really. You had a little snack. So that situation changed. So your metabolism is going
to make that range go up. So only for fasting glucose is
the number below 100 normal. Otherwise, it could be higher. Now consider a situation where
you’re taking a medication. Let’s say you’re on
a medication that causes your
potassium to go down. So you’re on a drug. It causes potassium
to leave your kidneys and go into the urine. Your potassium value
would then go down. I would expect it
to be lower, right? Because you’re taking
your medication. And so some of these
ranges are going to change, depending on what
medications you take, what you had for breakfast that
day, or not had for breakfast, what kind of medical
conditions you have. So it’s going to definitely
depend on the situation. So whenever you look
at ranges and values, and you want to see if you
are in the normal range, just consider all
these things that could explain why your
number may or may not be within that range.

43 thoughts on “Introduction to lab values and normal ranges | Health & Medicine | Khan Academy”

  1. Fantastic videos. I look forward to more of them. If possible, it would be nice with HD to make them look good for many years to come. I see you have made some already 🙂

  2. In love khan academy, studying for ccrn…critical care nursing exam with your videos. For the visual lerarner

  3. My supervisor does this at his other job. He's a lab technician with a 4-yr degree in Emergency Medical Philosophy. That's what they call it in the city I work in: Emergency Medical Philosophy, even though we do interns and hands-on training. Philosophy is theory if you ask me.

  4. thanks, what I'm looking for is something that would tell me how the average American performs on their blood tests.  Based on the blood test results of my last physical exam, my doctor told me I am in the top 3% of people health-wise for my age.  I'm looking for something that would formalize that, where someone would look at the blood test results of all Americans and analyze where each person's results places them health-wise.  Any idea whether that exists and how I'd find it?

  5. Thanks for the helpful videos, I use these and with the mobile app "Nclex Nursing Tools." Thanks a bunch..

  6. My old doctor should have watched this, when she said my labs were normal when they weren't. Some M.Ds these days…. Sad thing is I also work in the medical field and had a suspicion that she was wrong, however, I decided to trust her. Any how, don't for get about Globulin, Albumin and Total Protein, very important when looking at the liver, increased Globulin can mean liver inflammation, low Albumin symptom of severe liver disease and total Protein the two combined. There should be a A/G ratio 0.8-2.0/2.2 with 1.8-.2.0 being optimal.

  7. thanks for useful video. Can i repost your video with translation in my language in my blog, so it can help a lot of Medical students in my country- VietNam?

  8. Where could we obtain a pdf/word document of the paper with all the lab values on it? I like how the one you used is set up. This video is super helpful!

  9. @med_ideological ( is a page on instagram which focuses on nurturing & constantly reminding medical personnels (pregraduate to postgraduate levels). They’ve started posting concise, yet simple & comprehensible content on the most important basic sciences (anatomy & physiology) after that they’re preceding onto cover fun and educational facts for intermediates, semi-finalists, finalists & postgraduates) on pathology & medical cases (symptoms, diagnosis, treatments etc). Following this page means that whenever you are on instagram, you are always treating yourself with healfthy medical reminders and knowledge as well as enjoying your usual social content.

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