Why your head hurts: the most common causes and the danger signs

When your head hurts, you want two things fast: a likely explanation and a plan. Most headaches are “primary” (a problem with pain signaling itself), like tension-type or migraine. Others are “secondary,” meaning something else is wrong, from sinus infection to a rare emergency. Below, you’ll learn the main patterns doctors look for, simple steps that help at home, and the red flags that mean you should get medical care now.

What usually causes a headache?

Doctors first sort headaches into two broad groups. Primary headaches—tension-type, migraine, and cluster—are disorders of pain signaling in the head and neck. Secondary headaches are symptoms of another problem (for example, infection, head injury, very high eye pressure, or bleeding). This framework comes from the National Institute of Neurological Disorders and Stroke, which also notes that stress, sleep changes, foods or smells, and some medicines can trigger attacks in susceptible people (NINDS).

If you’re trying to make sense of a new or recurring symptom, our guide on how to make sense of symptoms can help you think through timing, severity, and context before you see a clinician.

How do common headache types differ?

Here are hallmark patterns clinicians use at the visit. These features don’t replace a diagnosis but can point you in the right direction.

Type	Typical pain and location	Other clues	Usual duration
Tension-type	Mild to moderate, pressing or tightening, often on both sides	Not usually with nausea; may have scalp or neck muscle tenderness	30 minutes to hours
Migraine	Moderate to severe, throbbing or pulsating, often one-sided	Nausea and/or sensitivity to light and sound; some people have aura (visual or sensory changes) before pain	4–72 hours
Cluster	Severe, one-sided, often around or behind one eye	Eye redness/tearing, stuffy or runny nose on the same side; attacks come in bouts (clusters)	15 minutes to 3 hours

These distinguishing features are summarized by the National Institute of Neurological Disorders and Stroke.

Which signs point to a more serious (secondary) cause?

Seek urgent care if you notice any red flags:

• A sudden, severe “thunderclap” headache that peaks within a minute.
• Fever, stiff neck, rash, or confusion (possible meningitis). The CDC lists fever, stiff neck, and headache as common meningitis symptoms and urges immediate medical attention (CDC).
• Headache after a head injury; headache with new neurologic symptoms (weakness, vision loss, trouble speaking), new seizure, or change in consciousness; new headache in pregnancy or after age 50; or headache with eye pain and vision changes (possible acute glaucoma). Family physicians group these as red flags that warrant prompt evaluation (American Family Physician).
• A new or progressively worsening pattern if you have cancer, HIV, or are immunosuppressed—get medical care. This is also flagged in primary-care diagnostic approaches.

MedlinePlus gives practical “when to call the doctor” lists that echo these warnings, including head injury and headache with neurologic changes (MedlinePlus Medical Encyclopedia).

What can you try at home for likely primary headaches?

• Track patterns. Note sleep, meals, fluids, stress, menstruation, and exposures (strong smells, certain foods). Triggers commonly interact with primary headaches, especially migraine.
• Build basics: regular sleep, meals, hydration, and movement. These steady routines often reduce attacks in primary headache disorders.
• Use over-the-counter pain relievers carefully. NINDS cautions that frequent use of acute pain medicines can worsen headaches or cause new daily symptoms, so discuss a plan for safe use and prevention with a clinician.
• Consider your other symptoms. If head pain comes with ongoing low mood, poor sleep, fatigue, or body aches, address those too—MedlinePlus notes stress, anxiety, sleep problems, and posture as common contributors to tension-type headaches (MedlinePlus: Tension headache).

If constant tiredness is part of the picture, you might explore common causes of persistent fatigue with your clinician.

How will a clinician narrow down the cause?

Expect questions about timing (sudden or gradual), frequency, triggers, prior history, other symptoms, and medicines you use. A neurologic exam helps spot warning signs. Imaging isn’t routine for classic primary headaches; it’s guided by red flags and exam findings. This diagnostic approach is outlined for primary care by family physicians.

How do you know if your plan is working?

• Over the next 2–4 weeks, your diary should show fewer or less intense headaches, or quicker relief with your chosen medicine and routines.
• If you still need frequent pain relievers, or headaches are happening most days, talk with a clinician about prevention and whether medication overuse could be part of the problem. NINDS advises making a plan to avoid overuse and explore preventive options.
• Seek care immediately if any red flag appears—MedlinePlus provides clear lists for when to call or go to the ER.

The bottom line for most people

Most headaches are primary and improve with steady routines, careful use of pain relievers, and trigger management. But headaches with red flags—sudden and severe, with stiff neck and fever, after head injury, with new neurologic symptoms, during pregnancy, or with eye pain and vision changes—need urgent medical care. CDC highlights fever, stiff neck, and headache as meningitis warning signs.