Diagnostic Approach to Fatigue in Primary Care (Updated 2026)
Fatigue can be one of the more overwhelming chief complaints in primary care because the differential is so broad. It could be related to sleep, medications, anemia, depression, or a recent illness—or it could be a clue to a more significant underlying condition.
In this episode, I walk through a systematic approach to evaluating fatigue in primary care, including how I organize the history, the questions that help narrow the differential, red flags and associated symptoms to look for, the focused physical exam, and how to decide what initial testing is appropriate.
2026 Update: Originally published in 2022 and reviewed for clinical accuracy in 2026. The overall approach to evaluating fatigue remains current. Updates include current fatigue duration definitions, thyroid testing recommendations, and follow-up when the initial evaluation is unrevealing. See the Clinical Updates as of 2026 below the video. For the current step-by-step approach, see the updated Fatigue Evaluation Cheat Sheet in the Digital NP Binder.
Listen
Watch
What I Covered in This Episode
How the duration and trajectory of fatigue help guide the initial evaluation
The history questions I ask when fatigue is the chief complaint
Why medications, supplements, substance use, sleep, caffeine, and psychosocial factors matter
Screening for depression and anxiety
How associated symptoms help narrow a broad differential
Important cardiopulmonary, infectious, neurologic, endocrine, rheumatologic, hematologic, and renal considerations
What to focus on during the physical exam
How I approach initial laboratory testing and when additional testing should be guided by the patient's history and exam
Clinical Updates as of 2026
Current duration definitions are: acute ≤1 month, subacute 1–6 months, and chronic >6 months.
Correction: Do not routinely include order Total T3 in the initial fatigue workup. I mention checking TSH, free T4, and possibly total T3 in this episode. For an initial thyroid evaluation in a patient presenting with fatigue, start with TSH with reflex to Free T4. Additional thyroid testing depends on the TSH result and clinical context. For more support in interpreting and managing thyroid labs, check out our Thyroid Lab Interpretation & Management for Primary Care.
If the initial evaluation is unrevealing, follow-up matters more than an indiscriminate workup. Reassess persistent unexplained fatigue and pursue additional testing when new localizing symptoms or findings emerge.
For the current step-by-step approach, see the updated Fatigue Evaluation Cheat Sheet in the Digital NP Binder.
Key Takeaways
Start by clarifying what the patient means by “fatigue.” They may be describing true fatigue/easy fatigability, sleepiness, weakness, or cognitive/mental fatigue—and that distinction can change where the evaluation goes next.
Fatigue is broad, so look for clues that narrow the differential. The onset, trajectory, associated symptoms, and impact on daily activities can help point you toward the most likely causes.
Sleep deserves a real history. Ask how much the patient is sleeping, whether sleep is disrupted, whether they wake feeling rested, whether they snore, and about caffeine or other factors affecting sleep.
Review everything the patient is taking. Prescription medications, OTC medications, supplements, alcohol, cannabis, opioids, stimulants, and other substances can all contribute to fatigue.
Screen for depression and anxiety—but don't assume fatigue is psychological. Use the history, screening tools, and the rest of the clinical picture to evaluate these alongside medical causes.
Use associated symptoms to decide where to look next. Dyspnea, chest pain, edema, fever, night sweats, weight changes, bleeding, neurologic symptoms, muscle weakness, and other findings can substantially narrow the workup.
Testing should answer a clinical question. Start with an appropriate initial evaluation, then let the history, exam, and results determine whether additional testing is actually needed.
Fatigue may take more than one visit to figure out. When the initial evaluation doesn't reveal a cause, and the patient is stable, follow-up and reassessment are part of the diagnostic process—not a failure to find the answer the first time.
Want a Quick Reference for Evaluating Fatigue?
Fatigue can be tough to work through in real time when the differential feels endless. The Fatigue Evaluation Cheat Sheet gives you a quick-reference approach to help you clarify what the patient means by fatigue, identify concerning findings, work through the differential, choose an appropriate initial workup, and decide what to do when the cause isn't immediately clear. Get your copy inside the Digital NP Binder.
Resources mentioned in this episode:
If you liked this post, also check out:
-
WEBVTT
1
00:00:08.580 --> 00:00:16.560
Hey there, welcome to the Real World NP podcast. I'm Liz Rohr, family nurse practitioner, educator,
2
00:00:16.800 --> 00:00:22.740
and founder of Real World NP, an educational company for nurse practitioners in primary
3
00:00:22.740 --> 00:00:29.120
care. I'm on a mission to equip and guide new nurse practitioners so that they can
4
00:00:29.120 --> 00:00:34.800
feel confident, capable, and take the best care of their patients. If you're looking for clinical
5
00:00:34.800 --> 00:00:40.680
pearls and practice tips without the fluff, you're in the right place. Make sure you subscribe and
6
00:00:40.680 --> 00:00:46.060
leave a review so you won't miss an episode. Plus you'll find links to all the episodes with
7
00:00:46.060 --> 00:00:59.420
extra goodies over at realworldnp.com slash podcast. So in this week's episode, I'm going
8
00:00:59.420 --> 00:01:06.300
be talking about the diagnostic approach to fatigue in primary care. So I just want to
9
00:01:06.300 --> 00:01:12.780
normalize it. This is a really tricky differential diagnosis because it's super broad and it's
10
00:01:12.780 --> 00:01:16.800
another one of those chief complaints where it could be something that's non-acute and
11
00:01:16.800 --> 00:01:21.740
not life-threatening or it could be a little bit more on the acute life-threatening side.
12
00:01:22.140 --> 00:01:28.220
So it just adds a little bit of stress to that hugely broad differential diagnosis. So
13
00:01:28.220 --> 00:01:33.960
the way I'm going to have this episode is that I'm going to focus on the initial approach,
14
00:01:34.340 --> 00:01:40.240
the history questions, the general categories of differential diagnosis, and then the approach
15
00:01:40.240 --> 00:01:47.240
to the physical exam and the testing. So as part of this episode, I made a cheat sheet and
16
00:01:47.240 --> 00:01:51.800
that is actually inside the digital NP binder. So if you would like to purchase a copy,
17
00:01:52.460 --> 00:01:57.980
the link is down below this video. However, feel free to take some notes as we go. In the
18
00:01:57.980 --> 00:02:01.660
cheat sheet, we talk a little bit more about the differential diagnoses to watch out for
19
00:02:01.660 --> 00:02:06.180
as a quick reference at your desk. So that's an option if you'd like it. So the first
20
00:02:06.180 --> 00:02:10.759
branching point that you want to assess for is, is this an acute fatigue, meaning
21
00:02:10.759 --> 00:02:16.860
is it in the last couple of days, weeks to a month, or is it more in that subacute
22
00:02:16.860 --> 00:02:23.780
to chronic stage? Is it a month or longer? For acute fatigue, it is more likely associated
23
00:02:23.780 --> 00:02:29.900
with things like stress or an acute illness, respiratory or otherwise. So that's more of the
24
00:02:29.900 --> 00:02:34.280
focus of where you want to look, although could still be the same thing as chronic,
25
00:02:34.400 --> 00:02:38.520
right? We'll talk, we'll, we'll get into it. We'll talk about it, but that's like your
26
00:02:38.520 --> 00:02:43.980
initial branching point. The other place to start in your history is with old cart. I
27
00:02:43.980 --> 00:02:50.260
talk about this all the time. That is my specific approach to obtaining a history in, in
28
00:02:50.260 --> 00:02:55.420
any visit that is a symptom based visit. So this is again, onset, location, duration,
29
00:02:55.820 --> 00:03:00.720
characteristics, associated factors, relieving factors, and either time or treatment or both.
30
00:03:00.880 --> 00:03:05.120
I usually ask both. But when you can always use that as your framework for any chief
31
00:03:05.120 --> 00:03:09.820
complaint specific to fatigue, though, you want to ask about, is this like a gradual
32
00:03:09.820 --> 00:03:15.480
onset? Was it a sudden onset? Like what are the other associated symptoms that you
33
00:03:15.480 --> 00:03:20.980
is it just fatigue by itself or do you have other physical issues, which we'll talk about
34
00:03:20.980 --> 00:03:25.140
in a second. But those are kind of like the main places that I'm starting with fatigue,
35
00:03:25.260 --> 00:03:30.160
in addition to all of those questions. And then the next place that I go to is what
36
00:03:30.160 --> 00:03:36.420
medications are they taking? Prescribed, over the counter, supplements or substances that
37
00:03:36.420 --> 00:03:42.560
they're using, marijuana, heroin, cocaine, et cetera. Those are really crucial to ask about
38
00:03:42.560 --> 00:03:47.200
when it comes to fatigue, because those contribute so often to their symptoms.
39
00:03:47.860 --> 00:03:52.240
And whenever we ask about those things, we also want to clarify how much are they using,
40
00:03:52.540 --> 00:03:58.120
what quantity, right? Can we get really specific about that? How often and whether it's
41
00:03:58.120 --> 00:04:03.560
every day or an approximation, right? How much alcohol are they using? How often are they using
42
00:04:03.560 --> 00:04:09.020
this herbal supplement since when, right? And then another thing, again, I always ask,
43
00:04:09.020 --> 00:04:13.460
I kind of tie it in with old cart, but it's like a status report. Is this getting worse?
44
00:04:14.000 --> 00:04:18.360
Is it getting better? Is it staying the same? Has it not changed at all throughout the whole
45
00:04:18.360 --> 00:04:22.920
time? And that is a really helpful snapshot for the trajectory of where we're going.
46
00:04:23.100 --> 00:04:27.240
This just started and it's getting really bad and I'm short of breath, right? That's
47
00:04:27.240 --> 00:04:30.720
very different than like, oh, I've had this fatigue for like a year. Basically, I've had
48
00:04:30.720 --> 00:04:34.440
this fatigue since COVID started, right? So those are very different contexts.
49
00:04:34.580 --> 00:04:38.420
The next thing you want to ask about that's so important for fatigue is asking about their
50
00:04:38.420 --> 00:04:43.900
hygiene. And I just feel like this cringe at the phrasing of sleep hygiene because it just,
51
00:04:44.380 --> 00:04:48.620
I don't know, it just feels like it's like, oh, really? But like, no, it's actually really
52
00:04:48.620 --> 00:04:52.640
important and it's not that hard to ask about, right? And it is actually like meaty and
53
00:04:52.640 --> 00:04:57.940
important, right? So what time do they go to sleep at night? Do they go to bed at the same
54
00:04:57.940 --> 00:05:02.080
time every night or is it different every night? When do they wake up? How many hours
55
00:05:02.080 --> 00:05:06.240
of sleep are they getting? Is it the same all the time or does it vary? Why is it varying?
56
00:05:06.240 --> 00:05:10.140
Is it because they work night shift? Is it because they have a newborn at home? Is it
57
00:05:10.140 --> 00:05:13.680
because they're waking up in the middle of the night to go to the bathroom, right? Like,
58
00:05:13.680 --> 00:05:17.020
getting into that will give you a lot of information about where you go next with
59
00:05:17.020 --> 00:05:22.680
your questioning. Another thing I ask patients, do they feel rested in the morning or do they
60
00:05:22.680 --> 00:05:28.300
feel like more fatigue during the day? Is it there all the time? Do they snore at night? Is
61
00:05:28.300 --> 00:05:33.380
there anybody at home that could tell them if they snore? More context around their bedtime
62
00:05:33.860 --> 00:05:39.580
Do they take anything to go to sleep at night? Do they have a dark, cool place to sleep, which
63
00:05:39.580 --> 00:05:43.900
is kind of like best practice for sleep hygiene? Do they use any caffeine? That's kind of the
64
00:05:43.900 --> 00:05:48.540
next part of sleep hygiene. What are they using? How much? How often, right? So coffee, tea,
65
00:05:48.600 --> 00:05:53.280
soda. Is it in the morning? Is it at night? Is it every day, right? I don't ask it this
66
00:05:53.280 --> 00:05:57.180
fast, but I tend to give patients these kinds of options when I'm doing my history, because
67
00:05:57.180 --> 00:06:01.360
again, it's a lot of questions to ask and it's a lot of information to get to. So it gives
68
00:06:01.360 --> 00:06:05.220
them an example of what I'm looking for, the general gist of it, right? So they're not just
69
00:06:05.220 --> 00:06:10.900
like, uh, I don't know, yes. So depression screening, that is the next kind of most
70
00:06:10.900 --> 00:06:18.540
important thing with fatigue. So often, anecdotally speaking, of course, most of the time
71
00:06:18.540 --> 00:06:26.060
it's either related to depression or anxiety, related to their sleep and sleep habits,
72
00:06:26.800 --> 00:06:30.280
and then anemia is another one too. But it's really important to assess for depression.
73
00:06:30.280 --> 00:06:35.860
I'll talk about anemia in a second, but you have to ask. I mean, one of the ways that
74
00:06:35.860 --> 00:06:39.800
to make this easier, and again, this is a longer visit sometimes because there's so many
75
00:06:39.800 --> 00:06:44.060
history questions, they may or may not volunteer all of the answers. So you have to ask a lot
76
00:06:44.060 --> 00:06:48.260
of things. Sometimes it's apparent, sometimes it's not, right? And so you want to ask about
77
00:06:49.440 --> 00:06:53.840
depression and anxiety symptoms. But I also do a screener for my literate patients,
78
00:06:53.900 --> 00:06:57.600
or I get assistance from my medical assistant to help a patient fill it out if they are not
79
00:06:58.100 --> 00:07:02.600
literate. Um, and it's also in multiple languages is called the PHQ-9. If you haven't used that
80
00:07:02.600 --> 00:07:08.080
already, that's the depression screener that I use. There's also the GAD-7, which is
81
00:07:08.080 --> 00:07:12.480
generalized anxiety disorder, seven questions. They're both available in multiple languages,
82
00:07:12.500 --> 00:07:17.440
which is helpful. It's a, it's a screening tool, right? It's not necessarily a diagnostic
83
00:07:17.440 --> 00:07:21.760
tool, but it's nice to kind of start that conversation of like, is this contributing
84
00:07:21.760 --> 00:07:29.300
potentially to your fatigue? The other kind of like main, most common causes of fatigue that
85
00:07:29.300 --> 00:07:35.380
you want to think about are, again, anemia comes up so often. So we want to ask like some
86
00:07:35.380 --> 00:07:39.720
history questions around that. Do they have any, have they had anemia in the past? Um,
87
00:07:39.720 --> 00:07:43.300
do they have any risk factors for anemia like menorrhagia, things like that, depending
88
00:07:43.300 --> 00:07:45.820
on the patient in front of you. And I'm looking at my notes. That's why I'm looking
89
00:07:45.820 --> 00:07:52.480
here. Um, you want to ask about, well, let's get into the body systems, right? So at this point,
90
00:07:52.520 --> 00:07:56.740
hopefully in your questioning, your line of questioning, you have some sort of inkling
91
00:07:56.740 --> 00:08:03.200
of like what body system we're talking about. Maybe you don't, maybe you do. Hopefully you do
92
00:08:03.200 --> 00:08:07.220
because then you can kind of steer your questioning in that direction. However,
93
00:08:07.220 --> 00:08:10.980
if you don't have a clear picture, then you kind of just have to go back to square one
94
00:08:10.980 --> 00:08:16.860
of like, what are the, what are the, what are the general body categories that we're thinking
95
00:08:16.860 --> 00:08:21.900
of that could contribute to fatigue? So honestly, you can just do a full ROS and you
96
00:08:21.900 --> 00:08:25.620
could even do like a full head to toe assessment if you wanted to just to like cover your bases.
97
00:08:27.560 --> 00:08:30.920
But there's, there's a, because the reason I'm saying that is because I'm going to go
98
00:08:30.920 --> 00:08:35.500
through the body systems, but there's a lot of them. So anyway, the hack is that you do
99
00:08:35.500 --> 00:08:38.820
all of them, right? But it lets, if we narrow in a little bit more, we're talking
100
00:08:38.820 --> 00:08:43.840
about red flags here, right? So we're thinking about cardiac. There are any, again,
101
00:08:44.080 --> 00:08:46.820
differentials aside, it's more specific in the cheat sheet and the binder,
102
00:08:47.260 --> 00:08:51.660
but differentials aside, anything cardiovascular wise, what are the simple, the questions you
103
00:08:51.660 --> 00:08:57.640
would ask? Shortness of breath, chest pain, edema, et cetera. Pulmonary, helpful to know,
104
00:08:57.760 --> 00:09:01.500
right? Hopefully they've volunteered some symptoms. Infectious, which is like any
105
00:09:01.500 --> 00:09:06.260
body system, right? Fever, chills, night sweats, lymphadenopathy. What are the risk
106
00:09:06.260 --> 00:09:10.980
factors there? We want to think about neurologic, neurologic and musculoskeletal. Again,
107
00:09:11.140 --> 00:09:16.740
even if you don't know the differentials of the neurologic diagnoses, can we do a neurologic
108
00:09:16.740 --> 00:09:21.940
exam, neurologic review of systems? And can we, if they have any muscle symptoms,
109
00:09:22.000 --> 00:09:25.560
can we do like a muscular exam for their strength or weakness, things like that?
110
00:09:25.700 --> 00:09:30.240
I've already mentioned psychological asking about depression, anxiety, other mental
111
00:09:30.240 --> 00:09:37.380
illnesses or symptoms of other mental illnesses. The two other big, two to three, it's like it
112
00:09:37.380 --> 00:09:41.480
could be anything, right? But you want to think about endocrine. Again, even if you don't know
113
00:09:41.480 --> 00:09:48.660
the differentials, hypothyroidism, do they have any heat, cold intolerance, any sort of like
114
00:09:48.660 --> 00:09:54.420
weight gain, things like that. Rheumatologic, again, fancy diagnoses aside, do they have any
115
00:09:56.300 --> 00:10:02.100
rashes, other potential signs and symptoms. And then I have to throw in renal. I'm obsessed with
116
00:10:02.560 --> 00:10:07.820
nephrology. It's not necessarily like your first symptom of renal impairment, but it could be.
117
00:10:08.560 --> 00:10:11.560
So yeah, so those are the body systems that we like red flag want to think about,
118
00:10:11.580 --> 00:10:15.400
especially cardiac and pulmonary, right? And infectious, right? What are the things that
119
00:10:15.400 --> 00:10:21.100
could get worst, the fastest? So when you get to your physical exam, you want to focus
120
00:10:21.100 --> 00:10:26.560
again on those body systems. Cardiac, pulmonary, you want to do a thyroid exam. You want to check
121
00:10:26.560 --> 00:10:32.460
for a lymphadenopathy. Again, depending on your ROS and your history, you want to do a neurologic
122
00:10:32.460 --> 00:10:36.220
exam. You want to do a strength assessment of their extremities if they're reporting any
123
00:10:36.220 --> 00:10:40.700
muscle pain or weakness. And obviously you want to look at their skin too, right?
124
00:10:41.700 --> 00:10:47.220
So there's a little bit of like a joke in like the real world community, not like this
125
00:10:47.220 --> 00:10:52.440
community, but like the real world of healthcare that a lot of patients come in with fatigue
126
00:10:52.440 --> 00:10:57.260
providers of any type, right? Not just nurse practitioners, physicians, PAs, DOs, et cetera.
127
00:10:57.600 --> 00:11:01.880
Providers will do labs to like buy some time because it's like not very clear what they're
128
00:11:01.880 --> 00:11:06.060
coming in for. So like just to normalize, like sometimes you'll go through all of these
129
00:11:06.060 --> 00:11:10.540
questions and it's like not that apparent what it could be going on. We do want to do a
130
00:11:10.540 --> 00:11:14.880
lab assessment regardless. We want it to be a targeted lab assessment based on our history
131
00:11:14.880 --> 00:11:19.680
and our physical exam findings, but just know that that's like a very common thing.
132
00:11:20.420 --> 00:11:24.680
Unfortunately, there aren't like guidelines that are guiding specific like, oh, for fatigue,
133
00:11:24.700 --> 00:11:29.380
you want to do these labs. It's really dependent on the differentials and your history taking,
134
00:11:29.380 --> 00:11:33.360
right? But for the most part, patients who have fatigue, you're going to focus on things like
135
00:11:33.360 --> 00:11:37.780
a CBC with differential, right? Because we're looking for some sort of anemia or heme
136
00:11:37.780 --> 00:11:43.360
malignancy or potential issue there. We want to do a complete metabolic panel because we
137
00:11:43.360 --> 00:11:48.980
look at again, liver, kidneys, electrolyte abnormalities, which might point to some
138
00:11:48.980 --> 00:11:56.500
endocrine abnormalities, TSH, free T4, perhaps total T3. And then the rest of them are really
139
00:11:56.500 --> 00:12:00.820
dependent on the patient in front of you, right? So have they had have screening for HIV
140
00:12:00.820 --> 00:12:05.420
or are they at risk for HIV? Again, infectious is a potential option. Hepatitis C,
141
00:12:05.440 --> 00:12:08.700
have they been screened for hepatitis C or do they have risk factors for that? Everybody
142
00:12:08.700 --> 00:12:15.360
should have HIV and Hep C at some point baseline, right? Do they need a urinalysis? Are they at
143
00:12:15.360 --> 00:12:20.600
risk for a UTI? Are they an older patient who might just have fatigue that is presenting,
144
00:12:20.640 --> 00:12:24.660
that's their presentation of their infection. And this is all up to your clinical judgment,
145
00:12:24.680 --> 00:12:29.360
right? But yeah, it's like, that's like the initial kind of like general approach,
146
00:12:29.380 --> 00:12:36.240
like first pass. And then again, other labs might be appropriate or other testing might be
147
00:12:36.240 --> 00:12:41.040
depending on the patient in front of you, their constellation of symptoms, what they've told you,
148
00:12:41.620 --> 00:12:45.600
things like that. So hopefully this is a helpful first approach to fatigue. Again,
149
00:12:45.600 --> 00:12:49.960
if you want to grab that cheat sheet inside the digital NP binder, the link is down below.
150
00:12:50.080 --> 00:12:53.460
Thank you so very much for watching. Hang in there and I'll see you soon.
151
00:13:10.970 --> 00:13:16.050
care to their patients. If you haven't gotten your copy of the ultimate resource guide for the
152
00:13:16.050 --> 00:13:22.570
new NP, head over to realworldnp.com slash guide. You'll get these episodes sent straight
153
00:13:22.570 --> 00:13:28.290
to your inbox every week with notes from me, patient stories and extra bonuses I really just
154
00:13:28.290 --> 00:13:32.930
don't share anywhere else. Thank you so much again for listening. Take care and talk soon.
Click Here for Your Ultimate Resource Guide for the New NP
Snag our favorite, time-saving, evidence-based resources to help you take the best care of your patients (while keeping your sanity). PLUS you'll get helpful articles, podcasts, and YT video episodes sent to your inbox every week or so.
© 2026 Real World NP. For educational and informational purposes only, see realworldnp.com/disclaimer for full details.
