What labs should a fatigue workup include?

A reasonable first layer: CBC, ferritin and iron saturation, TSH with free T4, B12, vitamin D, fasting glucose and insulin, HbA1c, a metabolic panel, and hs-CRP. The history then adds targeted pieces: a sleep study for snoring or unrefreshing sleep, orthostatic vitals for dizziness, celiac testing for GI symptoms, autoimmune serologies when joints, rashes, or family history point that way.

Can I be iron deficient if my hemoglobin is normal?

Yes. Iron deficiency runs through stages, and fatigue shows up in the early ones, long before anemia. Ferritin is the test that catches it. Many people, women with heavy periods most of all, live for years in the symptomatic gap between "ferritin above the lab cutoff" and "ferritin where you feel well."

How much fatigue is from poor sleep?

A lot of it. Unrefreshing sleep, snoring, waking at 3 AM, or a bed partner noticing pauses in breathing all point toward a sleep evaluation. Mild sleep apnea is common, underdiagnosed in women, and very treatable, and a home study is inexpensive and done in your own bed.

When is fatigue an emergency?

Fatigue with chest pain, shortness of breath at rest, fainting, new confusion, black stools, or rapid unexplained weight loss deserves urgent evaluation rather than a scheduled workup. When in doubt, ask; part of a direct primary care relationship is being able to send that message the same day.

Is "tired for months" ever just stress?

Stress and burnout cause fatigue, and they are on the differential from day 1. But calling it stress is a diagnosis of exclusion. Dana's story had a stress explanation available too, and taking it at face value would have left her iron deficient and sleep deprived. Rule the findable things out first; the labs and the sleep study are cheap compared to another year of exhaustion.

Why check fasting insulin when glucose and HbA1c are normal?

Insulin resistance begins with the pancreas working harder to keep glucose normal, so insulin rises years before glucose does. A normal HbA1c with a high fasting insulin is an early warning, and it maps directly onto the afternoon energy crashes patients describe. Catching it at this stage means food, muscle, and sleep changes still work, without medication.

What about cortisol and "adrenal fatigue"?

"Adrenal fatigue" is not a recognized diagnosis, and most patients who are told they have it turn out to have iron deficiency, sleep disorders, depression, or insulin resistance. Adrenal insufficiency, the condition that does exist, is rare and serious, and a morning cortisol is the right screen when the picture fits: weight loss, low blood pressure, salt craving, dizziness.

How fast should treated iron deficiency improve fatigue?

Energy usually starts improving within 4 to 6 weeks of consistent repletion, with steady gains out to 3 or 4 months as ferritin climbs. If ferritin rises and the fatigue does not budge, that is information too; it sends us back to the differential rather than to a higher iron dose.

What labs should a fatigue workup include?

A reasonable first layer: CBC, ferritin and iron saturation, TSH with free T4, B12, vitamin D, fasting glucose and insulin, HbA1c, a metabolic panel, and hs-CRP. The history then adds targeted pieces: a sleep study for snoring or unrefreshing sleep, orthostatic vitals for dizziness, celiac testing for GI symptoms, autoimmune serologies when joints, rashes, or family history point that way.

Can I be iron deficient if my hemoglobin is normal?

Yes. Iron deficiency runs through stages, and fatigue shows up in the early ones, long before anemia. Ferritin is the test that catches it. Many people, women with heavy periods most of all, live for years in the symptomatic gap between "ferritin above the lab cutoff" and "ferritin where you feel well."

How much fatigue is from poor sleep?

A lot of it. Unrefreshing sleep, snoring, waking at 3 AM, or a bed partner noticing pauses in breathing all point toward a sleep evaluation. Mild sleep apnea is common, underdiagnosed in women, and very treatable, and a home study is inexpensive and done in your own bed.

When is fatigue an emergency?

Fatigue with chest pain, shortness of breath at rest, fainting, new confusion, black stools, or rapid unexplained weight loss deserves urgent evaluation rather than a scheduled workup. When in doubt, ask; part of a direct primary care relationship is being able to send that message the same day.

Is "tired for months" ever just stress?

Stress and burnout cause fatigue, and they are on the differential from day 1. But calling it stress is a diagnosis of exclusion. Dana's story had a stress explanation available too, and taking it at face value would have left her iron deficient and sleep deprived. Rule the findable things out first; the labs and the sleep study are cheap compared to another year of exhaustion.

Why check fasting insulin when glucose and HbA1c are normal?

Insulin resistance begins with the pancreas working harder to keep glucose normal, so insulin rises years before glucose does. A normal HbA1c with a high fasting insulin is an early warning, and it maps directly onto the afternoon energy crashes patients describe. Catching it at this stage means food, muscle, and sleep changes still work, without medication.

What about cortisol and "adrenal fatigue"?

"Adrenal fatigue" is not a recognized diagnosis, and most patients who are told they have it turn out to have iron deficiency, sleep disorders, depression, or insulin resistance. Adrenal insufficiency, the condition that does exist, is rare and serious, and a morning cortisol is the right screen when the picture fits: weight loss, low blood pressure, salt craving, dizziness.

How fast should treated iron deficiency improve fatigue?

Energy usually starts improving within 4 to 6 weeks of consistent repletion, with steady gains out to 3 or 4 months as ferritin climbs. If ferritin rises and the fatigue does not budge, that is information too; it sends us back to the differential rather than to a higher iron dose.

Tired for Months, Labs 'Normal': The Workup That Found It | A Patient Case

TL;DR30-second take

A 41-year-old with 8 months of fatigue had been told her labs were normal after a TSH and a CBC. A full fatigue workup found 2 answers her checkup missed: a ferritin of 11 (iron deficiency that standard screening called 'normal' because she was not yet anemic) and fragmented sleep that a home study traced to mild sleep apnea. A proper workup covers iron studies with ferritin, a thyroid panel beyond TSH, B12 and vitamin D, fasting insulin and HbA1c, a sleep evaluation, orthostatic vitals, a depression screen, and a medication review. 'Tired for months' almost always has a findable cause; it just takes more than 12 minutes to find it.

A patient I will call Dana came to me at 41 with a story I hear more than any other.

She had been tired for about 8 months. Not sleepy after a bad night, but a heaviness that followed her through the whole day. Coffee at 7 AM on the walk to the El, coffee again at 2 PM, and still dragging by dinner. Her runs along the Delaware had turned into walks, and then stopped, because 20 minutes of jogging left her wiped out for the rest of the day.

She had done the responsible thing. She saw her doctor, who ordered a TSH and a blood count, and 2 days later the portal message came back: "Labs normal. Try to get more rest."

She didnt need more rest. She needed a better question.

Why "your labs are normal" was the wrong answer

The visit Dana got was not a bad visit. It was a 12-minute visit, and a 12-minute visit can only ask a 12-minute question: is this thyroid disease or anemia, yes or no?

Fatigue that lasts months has a much longer list of causes than that, and most of them will never show up on a TSH and a CBC. When I see a patient like Dana, the job is not to run 1 test and reassure. The job is to work the differential the way internal medicine is supposed to: history first, then a panel built to cover the territory.

What a fatigue history listens for

Before any blood is drawn, the story itself narrows things down. With Dana I wanted to know:

Sleep, in detail. Time in bed, time asleep, snoring, waking at 3 AM, how she felt at 7 AM. Dana slept "8 hours" but woke unrefreshed every single day, and her partner mentioned she had started snoring. That detail turned out to matter.
The shape of the fatigue. Worse after exertion, or steady? Fatigue that crashes for a day after mild exercise points one direction (toward post-exertional malaise and conditions like ME/CFS); fatigue that is simply constant points another.
Lightheadedness. Dizziness on standing, a racing heart in the shower or on stairs, would push me to check orthostatic vitals and think about POTS. Dana had none of this.
Periods. Dana's had gotten heavier over 2 years. This one sentence carried half the diagnosis.
Mood, medications, and life. Depression causes fatigue, and fatigue causes low mood; both deserve a validated screen, not a guess. Antihistamines, beta blockers, and sleep aids all cause fatigue too. Dana screened low for depression and took only an occasional allergy pill.

What the full panel included

Here is the workup we ran, and roughly why each piece was there:

Iron studies with ferritin and saturation, not just a CBC. You can be meaningfully iron deficient for years before you become anemic, and heavy periods are the most common reason.
A thyroid panel beyond TSH (free T4, and antibodies when the history suggests it), because early autoimmune thyroid disease can hide behind a normal-range TSH.
B12 and vitamin D, both common, both cheap to find, both miserable to live without. Philadelphia winters do our vitamin D levels no favors.
Fasting insulin, glucose, and HbA1c, because insulin resistance is one of the most common causes of afternoon crashes and it starts a decade before anything is called diabetes. This is the metabolic side of fatigue.
hs-CRP and a metabolic panel, screening for inflammation, liver, and kidney contributions.
A home sleep study, because of the snoring and the unrefreshing sleep. Blood tests cant see what happens at 3 AM.
Orthostatic vitals and a morning cortisol were on the list to add if the first layer came back empty.

What we found

Two things, and both had been sitting in plain sight.

Get Real Answers

Tired of being told your labs are 'normal'? Dr. Ash digs deeper.

Start Your Investigation

Her ferritin was 11. Her hemoglobin was normal, which is why the earlier CBC looked fine, but ferritin is the body's iron savings account, and hers was nearly empty. Iron deficiency without anemia causes fatigue, exercise intolerance, restless sleep, and brain fog, and it is missed constantly because many labs flag ferritin as "normal" anywhere above 10 or 15. For a menstruating woman with symptoms, the level where people tend to feel well is much higher, closer to 50 than to 11.

The home sleep study came back with mild sleep apnea. Not the dramatic kind, but enough to fragment her sleep into pieces all night, every night, which explained why 8 hours in bed kept producing exhausted mornings.

Neither finding is exotic. Thats the point. Most months-long fatigue is not a mystery illness; it is 1 or 2 common, treatable problems that nobody had time to look for.

The plan we built

Iron repletion with a target ferritin, rechecked at 8 and 16 weeks, and a plan with her OB-GYN for the heavy periods that caused the deficit in the first place.
Treatment for the sleep apnea, starting with the option she was most likely to use every night.
A graded return to her runs, once the iron came up, so the deconditioning of 8 months did not get blamed on something new.
A 90-day recheck to confirm the labs moved and, more important, that she felt like herself.

By the 90-day visit her ferritin was 62, the 2 PM coffee was optional, and she was running the Delaware trail again, slowly and happily.

What I want you to take from Dana's case

If you have been tired for months and someone told you your labs are normal, the honest translation is usually: the 2 tests we had time for are normal. A fatigue workup is not 1 tube of blood. It is a careful history, a panel built around your story, a sleep evaluation when the story points there, and a doctor with enough time to put the pieces together.

That is the kind of primary care this practice was built to do, and fatigue like Dana's is one of the most rewarding problems to solve, because it so often has an answer. You can read more about how we approach chronic fatigue, or get to know how I practice.

Key Takeaways

Months of fatigue with "normal labs" usually means the workup was 2 tests deep. A full evaluation covers iron studies with ferritin, thyroid beyond TSH, B12, vitamin D, fasting insulin and HbA1c, inflammation, sleep, orthostatic vitals, mood, and medications.
Ferritin is the fatigue test most often skipped. Iron deficiency without anemia is common, symptomatic, and treatable, and heavy periods are its most common cause.
Blood tests cannot see your sleep. Snoring plus unrefreshing sleep earns a home sleep study, and mild sleep apnea is badly underdiagnosed in women.
Dizziness or a racing heart on standing belongs in the history; it is the doorway to catching POTS early.
Most long fatigue is 1 or 2 common problems, found with time and a careful history, not a mystery illness.

Scientific References

Rosenthal TC, Majeroni BA, Pretorius R, Malik K. Fatigue: An Overview. Am Fam Physician. 2008;78(10):1173-1179.
Soppi ET. Iron Deficiency Without Anemia - A Clinical Challenge. Clin Case Rep. 2018;6(6):1082-1086.
Vaucher P, Druais PL, Waldvogel S, Favrat B. Effect of Iron Supplementation on Fatigue in Nonanemic Menstruating Women With Low Ferritin: A Randomized Controlled Trial. CMAJ. 2012;184(11):1247-1254.
Young T, Evans L, Finn L, Palta M. Estimation of the Clinically Diagnosed Proportion of Sleep Apnea Syndrome in Middle-Aged Men and Women. Sleep. 1997;20(9):705-706.
Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome; Institute of Medicine. Beyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness. National Academies Press; 2015.
American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes - 2024. Diabetes Care. 2024;47(Suppl 1):S1-S321.

Chronic Fatigue Treatment in Philadelphia - the full version of the workup this case walks through
Primary Care Physician in Philadelphia - the kind of visit where a history like Dana's has room to come out
POTS Treatment in Philadelphia - when fatigue comes with dizziness and a racing heart on standing
MCAS Treatment in Philadelphia - the allergic-inflammatory branch of the unexplained-symptoms differential
Metabolic Health in Philadelphia - fasting insulin, HbA1c, and the energy-crash side of fatigue
Meet Dr. Ash - who is doing the connecting-of-dots

Fishtown Medicine | Symptoms

2418 E York St, Philadelphia, PA 19125(267) 360-7927 hello@fishtownmedicine.comHSA/FSA Eligible

Start your intake

Frequently Asked Questions

Common Questions

Deep-Dive Questions

Two patterns raise my antennae: fatigue with a racing heart or lightheadedness on standing points toward POTS, which orthostatic vitals can screen for in 10 minutes; and fatigue that crashes hard for a day or more after mild exertion points toward post-exertional malaise, the hallmark of ME/CFS. Both are diagnoses with criteria, not labels of last resort, and both change the plan, because standard "exercise more" advice can make post-exertional malaise worse.

Ready when you are