A ferritin serum test is a blood test that measures the amount of ferritin in the blood, states Mayo Clinic. Ferritin is a protein that binds to iron, according to Healthline.
To prepare for the ferritin serum test, patients need to fast for about 12 hours, explains MedlinePlus. Doctors order the test to determine whether a patient has too little or too much iron stored in his blood. Symptoms of low ferritin levels include fatigue, chronic headache, dizziness, weakness, shortness of breath and ringing in the ears, according to Healthline. Symptoms of high ferritin levels include stomach pain, chest pain, heart palpitations and joint pain.