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Blood tests for tiredness What to check when you’re tired all the time

Feeling worn out most days is one of the most common reasons people see a doctor.1 Here’s what’s worth testing, what the results can and can’t tell you and what to do next.

7 tests $44.50 Results in 2 to 3 days

The short answer

If you’ve been tired for weeks and rest isn’t helping, seven blood tests check for the most common treatable causes: low iron, anemia, an underactive thyroid, high blood sugar and low vitamin B12.1,2 They also check your kidneys and liver, and add vitamin D to the same draw. Ask for ferritin, a complete blood count, TSH, HbA1c, vitamin B12, vitamin D and a metabolic panel.

Before you go
Fast for 12 hours. Water is fine, but skip food, coffee and tea. If you take biotin, stop it 3 days before.
If they’re normal
That still helps. It rules out the common causes these tests look for, so you can look at sleep, stress and medicines next.1,2
When not to wait
Call 911 for chest pain or trouble breathing. See a clinician right away if you’re also losing weight without trying, have fevers or night sweats or notice bleeding.9,10 All the signs
What it costs
$44.50 for all seven, from one blood draw. That’s the whole cost, and it’s HSA and FSA eligible.
The tiredness tests
$44.50 · 7 tests, one draw
Order

What the seven tests look for

Most check for a common cause that can be treated. All seven come from one blood draw.

  1. 01

    Low iron

    Ferritin test

    Low iron can tire you out even when your blood count is normal. In a trial of women with ferritin under 50 ng/mL and normal hemoglobin, iron eased tiredness more than a placebo did.3

    More likely if you have heavy periods, get breathless on stairs or don’t eat meat.

  2. It’s one of the causes doctors find most often in people who are tired.1,2

    More likely if you get breathless on stairs or have heavy periods.

  3. 03

    An underactive thyroid

    TSH test

    A high TSH means your body is pushing an underactive thyroid to make more hormone.5

    More likely if you also feel cold, have dry skin or constipation, or are gaining weight.5

  4. 04

    High blood sugar

    HbA1c test

    In one trial of tired patients, diabetes was the most common cause blood tests found, though only 4 in 173 people had it.2

    More likely if you’re thirsty a lot or peeing more than usual.6

  5. Low B12 can also cause pins and needles and memory problems.7

    More likely if you’re vegan, take metformin or acid reducers, or have had stomach surgery.7

  6. 06

    Low vitamin D

    Vitamin D test

    Your bones need vitamin D, and a long-term shortage weakens them.8 Almost 1 in 4 people in the US have a level that’s low or borderline,8 so a low result is common and won’t by itself explain tiredness. It’s on the list because it’s a cheap addition to the same draw.

    More likely if you get little sun, have darker skin or follow a vegan diet, and most worth knowing if you have a condition that affects how you absorb fat, such as celiac or Crohn’s disease, or have had weight-loss surgery.8

  7. 07

    Kidney, liver or calcium problems

    Metabolic panel test

    Kidney or liver problems and high calcium can all cause tiredness, so doctors usually include this panel in the first round of tests.1

What else causes tiredness?

Most tiredness that lasts has a cause no blood test shows: fewer than 1 in 10 people whose tiredness had no clear cause had one a blood test could find.2 Testing still helps, because it rules out the common causes these tests look for. These are the usual reasons for the rest, and what to do about each.

Sleep

Too little of it, or sleep apnea. Nearly 30% of US adults sleep under seven hours a night.1

If you snore or wake up unrefreshed, ask a clinician about a sleep test.

Stress and mood

Depression and anxiety are among the most common causes of tiredness that lasts.1

Tell a clinician how you’ve been feeling. It’s a real cause, and it can be treated.

Medicines and alcohol

Many medicines list tiredness as a side effect, and so does alcohol.1

Check the leaflet of anything you take every day.

Feeling worse after effort

If activity leaves you wiped out for a day or more, ask about ME/CFS. That crash is its defining symptom.1

Don’t push through it: with ME/CFS, exercise can make it worse.1

Don’t wait for a blood test if you also have

  • Chest pain, or breathlessness at rest
  • Fainting, or a racing or irregular heartbeat
  • Sudden weakness, confusion or trouble seeing
  • Weight loss you can’t explain
  • Fevers or drenching night sweats
  • Blood in your stool or urine, or black stools
  • A new lump or swelling
  • Swollen legs, or peeing much less than usual

Call 911 for chest pain, trouble breathing, fainting or sudden weakness. For the others, see a clinician right away.9,10 If you’re thinking about harming yourself, call or text 988.

How to get tested, and what it costs

Order the seven tests on their own, or get them inside a full yearly checkup. Either way it’s one blood draw, and the checkup adds a urine sample.

The tiredness tests
$44.50

The seven tests on this page, from one blood draw. Fast for 12 hours first.

Best if tiredness is the thing you want answered.

Order the seven tests
Base Core Annual
$213.25

The same seven, plus heart, hormone and iron tests and a urine test: a full yearly checkup. 23 tests. Fast for 12 hours first.

Best if you also want your heart risk and hormones checked, or it’s been a while since a checkup.

For women For men
  1. 01

    Order online

    Pick the seven tests or the full checkup. The price is the whole cost, and you can pay with an HSA or FSA card.

  2. 02

    Blood draw

    Fast for 12 hours first; water is fine. If you take biotin, stop it 3 days before. Go to any Labcorp location for free, or have blood drawn at home for $75.

  3. 03

    Get your results

    In the Picardo app in 2 to 3 days, with an explanation of each one. Ask Picardo what they mean, and book a physician follow-up if you want one.

Already tested, and still tired?

My ferritin was flagged normal

Many labs have flagged ferritin as normal down to about 15 ng/mL. Hematologists now count 30 ng/mL or under as iron deficiency in adults, and up to 50 if you’re tired, have heavy periods or another sign of low iron.4

Check your ferritin number

My TSH was normal

A normal TSH rules out most thyroid causes.5 Iron and B12 are the usual next checks, then sleep and stress.

Check your TSH number

Everything came back normal

That still tells you something: the common causes these tests look for are ruled out. Sleep, stress, medicines and recovering from an illness are next to look at.1,2

I’m bloated, or my gut is off

Ask about celiac disease. It can cause tiredness, and a blood test checks for it.1 Keep eating gluten until you’re tested, or the test can miss it.

Ask Picardo about your results. The app explains what each one means, and a physician can follow up if you want.

Questions people ask

What blood tests should I get if I’m always tired?

A complete blood count, TSH and a metabolic panel are the usual first checks.1 Ferritin, vitamin B12 and HbA1c look for three more common causes, low iron, low B12 and diabetes,2,3,7 and vitamin D is worth adding to the same draw.8

Can low iron make me tired if I’m not anemic?

Yes. In a trial of women with ferritin under 50 ng/mL and normal hemoglobin, 12 weeks of iron eased tiredness more than a placebo did.3 That’s why ferritin is on the list, not just a blood count.

Do I need to fast for these tests?

Yes, for 12 hours, because the metabolic panel measures your blood sugar. Water is fine, but skip food, coffee and tea. A morning appointment makes it easier. If you take biotin, which is in many hair, skin and nail supplements, stop it 3 days before: it can throw off the ferritin, TSH and B12 results.

How long should I wait before getting tested?

If rest hasn’t helped after a few weeks, it’s reasonable to test. In one trial, when doctors waited four weeks before ordering blood tests, most people didn’t come back.2

Can I get these tests without seeing a doctor first?

Yes. Order them online, get a blood draw at a Labcorp location or at home, and your results arrive in the Picardo app in 2 to 3 days. You can book a physician follow-up if you want to talk them through.

What happens if a result is off?

The app explains what it means and what usually comes next. The common causes are very treatable: iron for low iron,3 thyroid hormone for an underactive thyroid5 and B12 for low B12.7 A physician can follow up if you want one.

Should I test vitamin D for tiredness?

It’s worth adding to the same draw, which is why it’s one of the seven tests on this page, but don’t expect it to explain your tiredness. Almost 1 in 4 people in the US have a level that’s low or borderline,8 so a low result is common and won’t tell you why you’re tired. It matters most for your bones, and if you get little sun or have a condition that affects absorption.8

My results are normal. Why am I still tired?

Most lasting tiredness has a cause no blood test shows: fewer than 1 in 10 people whose tiredness had no clear cause had one a blood test could find.2 The usual reasons are sleep, stress, medicines and recovering from an illness. If effort leaves you wiped out for a day or more, ask about ME/CFS.1

Sources

  1. 1 Latimer KM, Gunther A, Kopec M. Fatigue in adults: evaluation and management. Am Fam Physician. 2023;108(1):58–69. www.aafp.org/pubs/afp/issues/2023/0700/fatigue-adults.html
  2. 2 Koch H, van Bokhoven MA, ter Riet G, et al. Ordering blood tests for patients with unexplained fatigue in general practice: what does it yield? Results of the VAMPIRE trial. Br J Gen Pract. 2009;59(561):e93–e100. doi.org/10.3399/bjgp09X420310
  3. 3 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. doi.org/10.1503/cmaj.110950
  4. 4 Powers JM, Lim MY, Achebe MO, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Adv. 2026;10(21):7353–7374. doi.org/10.1182/bloodadvances.2025015950
  5. 5 Garber JR, Cobin RH, Gharib H, et al. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Thyroid. 2012;22(12):1200–1235. doi.org/10.1089/thy.2012.0205
  6. 6 American Diabetes Association Professional Practice Committee for Diabetes. 2. Diagnosis and classification of diabetes: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S27–S49. doi.org/10.2337/dc26-S002
  7. 7 National Institute for Health and Care Excellence. Vitamin B12 deficiency in over 16s: diagnosis and management. NICE guideline NG239. London: NICE; 2024. www.nice.org.uk/guidance/ng239
  8. 8 Office of Dietary Supplements, National Institutes of Health. Vitamin D: fact sheet for health professionals. Updated June 27, 2025. Accessed October 29, 2026. ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
  9. 9 MedlinePlus. Fatigue. US National Library of Medicine. Reviewed May 2025. Accessed October 29, 2026. medlineplus.gov/ency/article/003088.htm
  10. 10 Cleveland Clinic. Fatigue. Accessed October 29, 2026. my.clevelandclinic.org/health/symptoms/21206-fatigue

Updated 4 Nov 2026.

This is general health information, not medical advice: talk to your clinician about your results and before changing any treatment.