Headaches are very common, with most people experiencing them at some point. While many headaches are not concerning, severe or persistent headaches may require medical evaluation. As part of this evaluation, doctors may recommend blood tests to help determine the cause of the headaches.
Why are blood tests done for headaches?
There are a few main reasons why doctors may order blood tests for headaches:
- To check for signs of infection – Headaches can sometimes be caused by infections like meningitis or encephalitis. These infections require prompt treatment, so doctors test the blood for signs of infection.
- To evaluate hormone levels – Headaches are often associated with hormonal changes and imbalances. Blood tests can help assess levels of hormones like estrogen in women.
- To check for anemia – Low red blood cell count (anemia) can lead to oxygen depletion in the brain and cause headaches. Blood counts provide information about anemia.
- To look for autoimmune disease – Some autoimmune disorders like lupus can cause inflammation in the blood vessels of the brain, resulting in headaches. Specific blood tests help diagnose autoimmune conditions.
- To rule out blood clots – Blood clots in the veins draining blood from the brain (venous sinus thrombosis) can cause headache. Tests like D-dimer assays help detect clotting.
- To check for abnormalities with blood vessels – Some headaches are caused by problems with the blood vessels in the brain. Tests can check for vessel abnormalities.
In many cases, blood tests are used to rule out potentially dangerous causes of headaches. Even if the tests are normal, they provide useful information to the doctor developing a treatment plan.
What are the most common blood tests done for headaches?
Some blood tests used to evaluate headaches include:
- Complete blood count (CBC) – Checks levels of red cells, white cells, and platelets. Helps diagnose anemia and infection.
- ESR (erythrocyte sedimentation rate) – Measures inflammation in the body. Elevated in conditions like autoimmune disease.
- C-reactive protein (CRP) – Another marker of inflammation. May be elevated with chronic headaches.
- Thyroid tests – Measure levels of thyroid hormones T3 and T4. Headaches are a symptom of hyper/hypothyroidism.
- Hormone tests – May include estrogen, progesterone, testosterone, etc. Assess for hormonal imbalances contributing to headaches.
- Vitamin D – Low vitamin D is linked with chronic headaches. Blood levels help identify deficiency.
- Metabolic panel – Checks electrolytes, kidney function, blood sugar. Electrolyte abnormalities can trigger headaches.
- Coagulation studies – Prothrombin time, partial thromboplastin time, and D-dimer tests help diagnose blood clots.
- Lipid panel – Measures cholesterol and triglycerides. High lipids increase stroke risk, a cause of headache.
Are there any specialized blood tests for headaches?
In some cases, doctors may order more specific blood tests to pinpoint the cause of headache:
- ANA (antinuclear antibody) – Positive in autoimmune disorders like lupus that can cause headaches.
- Rheumatoid factor – Elevated in rheumatoid arthritis and similar autoimmune conditions.
- Cerebral vasculitis panel – Tests for inflammation of arteries in the brain that can result in severe headache.
- Headache profile – Checks for multiple potential headache causes like food allergies, hormone imbalance, and inflammation.
- Serotonin level – Low serotonin levels are associated with migraines. Measuring blood serotonin may help diagnose migraines.
- Food allergy testing – Identifies immunoglobulin antibodies to foods. Some food allergies and sensitivities trigger headaches.
- Gluten antibodies – Measures antibodies to gluten. Can identify celiac disease, a cause of headaches.
- Genetic testing – Diagnose familial hemiplegic migraine, CADASIL disease, and other genetic headache disorders.
These specialized tests are not needed in every case but may be recommended if initial blood work and clinical evaluation suggests a specific headache cause.
What blood tests help diagnose common headache types?
Blood tests can assist in diagnosing some specific headache disorders:
Migraine Headaches
- Genetic testing for familial hemiplegic migraine
- Hormone tests to identify fluctuations triggering migraines
- Headache profile to assess neurochemical contributors
- Food allergy/sensitivity testing
Tension Headaches
- Complete blood count to check for anemia
- Vitamin D level to assess for deficiency
- Thyroid testing to rule out hypothyroidism
- ESR and CRP to measure inflammation
Cluster Headaches
- Serotonin testing
- Headache profile
- Hormone testing
- Blood oxygen level (hypoxia can trigger clusters)
Thunderclap Headaches
- Coagulation studies to check for blood clots
- Cerebral vasculitis panel
- ANA to test for autoimmune disorders
- ESR and CRP for inflammation
Exertional Headaches
- CBC, metabolic panel to check electrolytes
- Coagulation studies to rule out blood clots
- Cerebral vasculitis panel if suspicious of artery abnormalities
The right headache blood tests depend on the headache characteristics, associated symptoms, medical history, and doctor’s clinical judgement.
Are there any risks or downsides to headache blood tests?
Blood tests carry minimal risks but there are a few downsides to consider:
- Discomfort or bruising from the blood draw
- Low risk of infection at the IV site
- Dizziness or fainting from the blood draw
- Scar formation if blood veins are overused
- Chance of false positive results, leading to more invasive testing
- Added costs, often not covered by insurance unless doctor deems testing medically necessary
Headache patients and doctors should consider these potential downsides before ordering extensive blood workup. Targeted testing based on clinical presentation is best to maximize the benefit while minimizing risks and costs.
What are normal and abnormal ranges for headache blood tests?
Reference ranges for headache blood tests:
| Test | Normal Range | Abnormal Range |
|---|---|---|
| WBC (white blood cells) | 4,500-11,000 per mcL | Below 4,500 = leukopenia Above 11,000 = leukocytosis |
| Hemoglobin | 12-16 g/dL (women) 13.5-17.5 g/dL (men) |
Below range = anemia |
| Platelets | 150,000-450,000 per mcL | Below 150,000 = thrombocytopenia Above 450,000 = thrombocytosis |
| ESR | 0-30 mm/hr | Above 30 mm/hr = inflammatory process |
| CRP | Below 1 mg/dL | Above 1 mg/dL = inflammation/infection |
Results outside of normal ranges prompt further investigation for underlying headache causes.
How long does it take to get headache blood test results?
Most routine headache blood test results come back within 24-48 hours. More extensive testing can take 3-5 days for results.
Factors affecting turnaround time:
- Type of tests ordered – Simple CBC results come back quickest. Specialty tests take longer.
- Location of lab – On-site labs at hospitals provide fastest results. Off-site commercial labs are slower.
- Insurance paperwork and authorizations – Delays if additional insurance approval needed for specialized tests.
- How the results are delivered – Paper mail results take longer. Electronic medical record systems provide faster access.
- Urgent vs routine testing – Priority/stat testing speeds up results for medical emergencies.
Patients should follow up with their doctor for interpretation of headache blood test results. Treatment plans are adjusted based on the results.
Can blood tests miss the cause of headaches?
Yes, it is possible for blood tests to miss the underlying cause of headache even when abnormal results are found. Reasons include:
- False positive results – Abnormal results that are not actually related to the cause.
- False negative results – Normal test values even though headache cause is present.
- Testing done too early – Some abnormalities develop later and are missed on initial blood tests.
- Intermittent causes – Headache triggers that fluctuate and are not present at time of testing.
- Rare headache disorders – Uncommon causes not included in standard test panels.
- Other medical conditions – Headaches arising secondary to separate health issues.
- Medication side effects – Drug-induced headaches.
- Individual variation – Headache mechanism unique to the patient.
Blood tests provide useful information but clinical evaluation, imaging, and other testing may also be needed for accurate headache diagnosis. Doctors must interpret results in context of the patient’s full clinical picture.
What happens if a headache patient’s blood tests are normal?
If a patient’s headache blood tests are normal, additional steps include:
- Review if appropriate tests were ordered based on symptoms and history.
- Repeat blood tests after a period of time in case an abnormality develops later.
- Order specialized blood tests not included in initial workup.
- Refer patient to neurologist for expert assessment if cause remains uncertain.
- Investigate non-blood test causes like musculoskeletal issues, mental health disorders.
- Discuss and rule out medication side effects.
- Pursue neuroimaging studies like CT, MRI, or angiogram for further evaluation.
- Initiate symptom-specific treatment trial even without identifiable cause.
- Provide reassurance that testing ruled out dangerous headache causes.
Normal blood tests do not mean there is no real headache problem. Doctors work to identify the mechanism and customize treatment for headache relief.
Conclusion
Blood testing is a useful diagnostic tool to evaluate possible underlying causes of headaches. Tests like CBC, metabolic panels, inflammatory markers, and coagulation studies screen for common headache contributors. Targeted testing for autoimmune conditions, cerebral vasculitis, food allergies, hormone imbalance, and genetic mutations can provide insight in some cases. However, blood tests have limitations and may miss more obscure headache etiologies. They should be used as part of a comprehensive workup rather than the sole diagnostic strategy. With both normal and abnormal results, doctors must integrate blood test findings into the full clinical context to guide optimal headache management.