Headache and fatigue are two common health conditions that may have multiple causes. If the cause of your headache and fatigue is unknown, it is best to consider the simplest explanations first before moving on to more serious possibilities. If these symptoms do not go away after a few days, see your doctor to rule out additional causes.
Caffeine Withdrawal
Regular caffeine consumption causes a physical dependency, which can result in withdrawal symptoms such as headache and fatigue if you do not have caffeine at a usual time. Caffeine gives you more energy after consuming it, but it is typically followed by a crash approximately 24 hours later unless you have more caffeine, according to the University of Utah.
Dehydration
Mild dehydration can cause several health symptoms, including headaches, fatigue, dry mouth and muscle weakness. It is especially important to drink enough water if you are sick or engaging in moderate to strenuous exercise that may result in losing a lot of water. Don't rely on when you feel thirsty as a signal to drink more water; thirst is a sign that you are already dehydrated.
Viral Illness
Viral illnesses can cause headache and fatigue symptoms. Illnesses that can cause these symptoms range from the common cold and influenza to more serious conditions, such as viral meningitis and mononucleosis, which is also called the "kissing disease." Diagnosing which virus is causing your headache and fatigue depends on the other symptoms that may be occurring at the same time, such as sinus congestion, cough, nausea, diarrhea and fever.
Infections
Headache and fatigue following a viral illness may indicate the existence of a secondary bacterial infection, such as ear infections, bronchitis or pneumonia. Sinus infections are common following colds and may cause intense sinus pain and congestion in addition to headache and fatigue. Strep is a bacterial infection that also causes these symptoms. A bacterial infection will need a prescription for antibiotics from a doctor.
