Symptom → lab tests
What blood tests should you get for fatigue?
Short answer
Persistent fatigue has a short list of common, testable causes: an underactive thyroid, low iron stores, vitamin B12 or D deficiency, and blood-sugar problems. A first-pass workup is TSH, ferritin, vitamin B12, vitamin D and hemoglobin A1c, plus a CBC to rule out anemia. If those are normal, the next layer is hormones and inflammation.
Medically reviewed by Youmna DiStefano, MD · Last reviewed September 2026
When should you see a clinician instead of ordering a test?
- Fatigue with chest pain, shortness of breath at rest, or fainting
- Unintentional weight loss, fever, or night sweats alongside the fatigue
- Fatigue so severe you can't manage daily activities, or that came on suddenly
Why these tests for fatigue?
Fatigue is a symptom with many causes, and blood tests are how the common, fixable ones get found or ruled out. Thyroid hormone sets the body's metabolic pace, so an underactive thyroid (high TSH) is checked first. Ferritin reflects iron stores — low iron causes fatigue well before hemoglobin drops into anemia, especially in menstruating women and endurance athletes.
Vitamin B12 and vitamin D deficiencies are both common and both produce tiredness; hemoglobin A1c and fasting glucose catch blood-sugar problems that often show up as afternoon crashes. A CBC with differential screens for anemia and infection. When this first layer is normal, morning cortisol, testosterone (in men) and inflammation markers are the usual second look.
Which conditions do these tests help evaluate?
- Chronic Fatigue — Thyroid, iron, B12, vitamin D and inflammation markers for persistent tiredness.
- Anemia — CBC, iron studies, ferritin, B12 and folate to find the cause of fatigue and low energy.
- Thyroid Problems — TSH, Free T4/T3 and antibodies to evaluate an under- or over-active thyroid.
Which tests, and what do they cost?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Chronic Fatigue PanelSaves $77.92 vs ordering the tests separately | Panel · 9 tests | $169.99 | Yes | 3–5 business days |
| General Wellness PanelSaves $6.97 vs ordering the tests separately | Panel · 4 tests | $89.99 | Yes | 1–3 business days |
| TSH (Thyroid Stimulating Hormone) | Test | $26.99 | No | 1–3 business days |
| Ferritin | Test | $24.99 | No | 1–3 business days |
| Vitamin B12 | Test | $25.99 | No | 2–4 business days |
| Vitamin D, 25-Hydroxy | Test | $41.99 | No | 1–3 business days |
| Hemoglobin A1c | Test | $21.99 | No | 2–4 business days |
| CBC with Differential | Test · 14 biomarkers | $21.99 | No | 1–3 business days |
| Cortisol (AM) | Test | $26.99 | No | 2–4 business days |
Common questions
Which single test is most useful for fatigue?
There isn't one. TSH and ferritin together catch the two most common testable causes (thyroid and iron), which is why fatigue panels start with both and add B12, vitamin D and A1c.
Do I need to fast for fatigue blood work?
Only if the panel includes fasting glucose or a lipid panel. TSH, ferritin, B12, vitamin D and A1c do not require fasting; morning cortisol should be drawn before 9 a.m.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.