Feeling tired after a late night or a particularly busy week is normal. But what if you're getting enough sleep and still wake up exhausted?
Persistent fatigue is common, and there are many possible explanations. Stress, poor sleep, diet, medications, lifestyle and medical conditions can all play a role.
Sometimes, blood testing can provide useful information that may help you and your healthcare provider investigate what could be contributing to persistent tiredness.
Here are seven commonly ordered blood tests that may be considered when investigating fatigue.
1. Complete Blood Count (CBC)
A Complete Blood Count is one of the most commonly performed blood tests.
It measures several components of your blood, including red blood cells, white blood cells, hemoglobin, hematocrit and platelets.
One reason a CBC may be ordered when investigating fatigue is to look for abnormalities associated with anemia. Red blood cells help carry oxygen throughout the body, and abnormalities involving red blood cells or hemoglobin can sometimes be associated with tiredness, weakness or shortness of breath.
USLabTesting lists CBC testing as part of its general health and anemia-testing options.
→ Explore CBC and general health blood tests
→ Compare anemia testing options
2. Thyroid Testing
Your thyroid is a small gland in your neck, but the hormones it produces influence many processes throughout your body.
When thyroid hormone levels are abnormal, some people can experience symptoms such as fatigue, changes in weight, feeling unusually cold or hot, and difficulty concentrating.
A common starting point is a TSH (thyroid-stimulating hormone) test. Depending on the circumstances, additional thyroid markers may also be considered.
USLabTesting also lists health panels that combine thyroid testing with other commonly ordered tests.
→ View the Standard Health Panel including TSH, CBC and CMP
3. Vitamin B12
Vitamin B12 plays an important role in red blood cell formation and normal nervous-system function.
Low B12 levels can be associated with fatigue and weakness. More significant deficiencies may also produce neurological symptoms such as numbness or tingling.
People following certain diets and people with conditions or medications that interfere with B12 absorption may have a greater risk of deficiency.
A blood test can measure vitamin B12 levels.
→ Browse vitamin and nutritional blood tests
4. Vitamin D
Vitamin D is important for several functions within the body, including bone health.
The body can produce vitamin D when skin is exposed to sunlight, while smaller amounts can come from food and supplements.
People with limited sun exposure and certain other risk factors may have lower vitamin D levels.
A 25-hydroxy vitamin D blood test is commonly used to assess vitamin D status.
Fatigue alone doesn't mean you have a vitamin D deficiency, but laboratory testing can determine your vitamin D level.
→ Compare vitamin and nutritional tests
5. Iron and Ferritin
Iron is essential for producing hemoglobin, which helps red blood cells transport oxygen.
Ferritin is a protein that stores iron, and measuring ferritin can help assess the body's iron stores.
Depending on your circumstances, testing may include ferritin alongside measurements such as serum iron, total iron-binding capacity (TIBC) and transferrin saturation.
Because iron deficiency can have numerous causes, abnormal results should be discussed with a healthcare professional rather than simply assuming supplementation is appropriate.
→ Compare anemia and related blood tests
For people looking for a broader group of tests, USLabTesting also lists a Comprehensive Health Panel containing CBC, CMP, iron and TSH testing.
→ Browse comprehensive/general health testing
6. Comprehensive Metabolic Panel (CMP)
Sometimes the best place to start isn't with one specific vitamin or hormone.
A Comprehensive Metabolic Panel measures multiple substances in your blood and provides information related to areas including:
Blood glucose
Electrolytes
Kidney function
Liver function
Blood proteins
Calcium
Because fatigue can have many possible causes, a broader panel can provide information across several areas at once.
→ Explore CMP and general health testing
USLabTesting also lists broader health panels combining a CMP with other commonly ordered tests.
→ View the Standard Health Panel
7. Testosterone
Testosterone testing may be appropriate in certain circumstances, particularly when fatigue occurs alongside other symptoms.
In men, symptoms associated with low testosterone can include reduced sex drive, changes in muscle mass and reduced energy.
However, fatigue by itself isn't enough to determine whether testosterone is low.
Testosterone levels can also vary according to factors such as age and time of day, so results need to be interpreted appropriately.
USLabTesting currently lists several testosterone testing options, including Total Testosterone, Free Testosterone, and Free & Total Testosterone tests.
→ Compare testosterone blood tests
Which Blood Test Should You Get?
There isn't one universal "fatigue blood test."
That's because fatigue isn't a disease—it's a symptom with many potential causes.
For one person, iron deficiency might be relevant. For another, thyroid function could warrant investigation. Someone else's bloodwork may be completely normal and their fatigue may have another explanation altogether.
If your fatigue is persistent, severe, unexplained or accompanied by other symptoms, consider speaking with a healthcare professional. They can help determine which tests may be appropriate based on your symptoms, medical history, medications and other factors.
Want to Compare Several Tests at Once?
If you're interested in several of the tests discussed above, purchasing them individually isn't necessarily the only option.
USLabTesting lists health panels that combine multiple laboratory tests. For example, the Standard Health Panel includes CBC, CMP, urinalysis, lipid testing and TSH.
→ View the Standard Health Panel
You can also browse a wider selection of wellness testing options:
→ Compare General Health & Wellness Tests
Can You Order Your Own Blood Tests?
Depending on the test and applicable requirements, consumers in many parts of the United States can purchase certain laboratory tests without first going through a traditional doctor's-office visit.
Prices and test contents can vary between providers, so it's worth checking exactly what's included before ordering.
USLabTesting helps consumers discover and compare laboratory testing options in one place.
→ Browse Lab Tests on USLabTesting
Before purchasing a test, check which biomarkers are included, whether fasting or other preparation is required, where specimen collection takes place and how you'll receive your results.
Important Medical Disclaimer
This article is for general informational purposes only and is not intended to provide medical advice, diagnosis or treatment. Fatigue can have many causes, including potentially serious medical conditions. Laboratory results should be interpreted in the context of your symptoms and medical history. Seek advice from an appropriately qualified healthcare professional if you have concerns about your health.