When Is a Headache Serious? Warning Signs to Know

What makes most headaches benign?

Headaches fall into two broad groups. Primary headaches — tension-type and migraine — have no dangerous underlying cause; the headache is the condition itself. Tension headaches produce a dull, squeezing band around the head and are the most common type overall. Migraines are often one-sided and throbbing, frequently accompanied by nausea or sensitivity to light and sound. Cluster headaches, less common, cause intense pain around one eye.

Secondary headaches are caused by something else — an infection, elevated blood pressure, medication overuse, or, rarely, a structural problem. The goal of clinical evaluation is to distinguish between these categories.

A headache is much more likely to be benign when it: - Feels exactly like headaches you have had many times before - Builds gradually over minutes to hours rather than seconds - Responds at least somewhat to over-the-counter pain relievers or rest - Has no accompanying neurological symptoms, fever, or stiff neck - Is not related to a recent head injury

Familiarity is meaningful: if you are a migraine sufferer and today's headache feels like your usual migraine, that is a real piece of reassurance — though new features in a familiar headache still deserve attention 1Ref 1Walling A (2020).Frequent Headaches: Evaluation and Management.Overview of primary vs secondary headache evaluation, when neuroimaging is indicated, medication overuse headache prevalence and management, and the clinical history as the cornerstone of diagnosis.

Which headaches need emergency care right now?

Any one of the following features changes a headache from 'probably fine' to 'needs immediate evaluation.' These are codified in the clinical SNNOOP10 framework used by neurologists to screen for serious secondary causes 2Ref 2Do TP, Remmers A, Schytz HW, et al. (2019).Red and orange flags for secondary headaches in clinical practice: SNNOOP10 list.The SNNOOP10 clinical framework for identifying secondary headache red flags including thunderclap onset, fever/neck stiffness, neurological deficits, new onset after age 65, and immunocompromised status.

The most critical is the thunderclap headache — a sudden, explosive headache that reaches maximum intensity within seconds or at most a minute. This is the classic presentation of subarachnoid hemorrhage (bleeding around the brain), a life-threatening emergency 3Ref 3Long D, Koyfman A, Long B (2019).The Thunderclap Headache: Approach and Management in the Emergency Department.Definition of thunderclap headache (peak intensity within 60 seconds), subarachnoid hemorrhage as the most dangerous etiology, and the CT-then-lumbar-puncture evaluation pathway in the ED. It cannot reliably be distinguished from a benign cause without imaging and, in some cases, a spinal tap.

Other emergencies: - Fever and stiff neck alongside headache suggest meningitis or encephalitis - New neurological symptoms — vision changes, weakness on one side, numbness, speech difficulty, or confusion - Headache following head injury or trauma - Loss of consciousness or near-loss of consciousness - New severe headache in someone with cancer, HIV, or immune suppression - A non-blanching rash with headache — this can indicate meningococcal disease - Headache in pregnancy with elevated blood pressure — possible preeclampsia - New onset headache in someone over 65 — secondary causes are more common in this group 2Ref 2Do TP, Remmers A, Schytz HW, et al. (2019).Red and orange flags for secondary headaches in clinical practice: SNNOOP10 list.The SNNOOP10 clinical framework for identifying secondary headache red flags including thunderclap onset, fever/neck stiffness, neurological deficits, new onset after age 65, and immunocompromised status

Do not drive yourself to the hospital if neurological symptoms are present.

What headache patterns need a scheduled visit — not the ER?

Some headache patterns do not call for emergency evaluation but do deserve a clinician appointment:

• Increasingly frequent headaches — more days per month than before, or headaches that have been steadily worsening over weeks 1Ref 1Walling A (2020).Frequent Headaches: Evaluation and Management.Overview of primary vs secondary headache evaluation, when neuroimaging is indicated, medication overuse headache prevalence and management, and the clinical history as the cornerstone of diagnosis
• Headaches that wake you from sleep — while some migraines can do this, a consistent pattern deserves evaluation
• Medication overuse headache — if you are taking pain relievers more than two or three days per week for headaches, you may be in a cycle where the medication itself is sustaining the problem. This is common and treatable, affecting an estimated 0.5–2% of the general population 4Ref 4Diener HC, Kropp P, Dresler T, et al. (2022).Management of medication overuse (MO) and medication overuse headache (MOH) S1 guideline.Medication overuse headache definition (analgesics ≥15 days/month or triptans/opioids ≥10 days/month), prevalence 0.5–2%, and withdrawal as the cornerstone of treatment
• New-onset headache after age 50 — the likelihood of a secondary cause is higher in this group
• Headache during or after pregnancy — particularly if blood pressure is elevated
• In people with cancer or HIV — a new headache warrants earlier evaluation

What will a clinician do for a headache?

A detailed history and neurological examination are the most important diagnostic steps — most headaches are diagnosed from the story and exam, not from imaging.

For most people with a clear primary headache pattern and no red flags, imaging (MRI or CT) is not needed. Imaging is reserved for specific situations: red flag features, new or changing patterns, or genuine uncertainty after history and exam 1Ref 1Walling A (2020).Frequent Headaches: Evaluation and Management.Overview of primary vs secondary headache evaluation, when neuroimaging is indicated, medication overuse headache prevalence and management, and the clinical history as the cornerstone of diagnosis.

For a thunderclap headache, a non-contrast CT of the head is done urgently; if CT is negative but subarachnoid hemorrhage is still suspected, a lumbar puncture (spinal tap) follows — blood in the cerebrospinal fluid or xanthochromia confirms hemorrhage 3Ref 3Long D, Koyfman A, Long B (2019).The Thunderclap Headache: Approach and Management in the Emergency Department.Definition of thunderclap headache (peak intensity within 60 seconds), subarachnoid hemorrhage as the most dangerous etiology, and the CT-then-lumbar-puncture evaluation pathway in the ED.

For established primary headache disorders like migraine, clinicians can offer targeted treatments: acute medications to stop an attack, and preventive medications if headaches are frequent. For medication overuse headache, the cornerstone of treatment is gradual withdrawal of the overused drug under clinical guidance 4Ref 4Diener HC, Kropp P, Dresler T, et al. (2022).Management of medication overuse (MO) and medication overuse headache (MOH) S1 guideline.Medication overuse headache definition (analgesics ≥15 days/month or triptans/opioids ≥10 days/month), prevalence 0.5–2%, and withdrawal as the cornerstone of treatment.

Keeping a headache diary helps your clinician

When headaches are frequent or you are uncertain of the pattern, tracking them for two to four weeks before a visit gives a clinician valuable information. Useful items to note include:

• Date, time, and duration
• Location and quality of pain (throbbing, pressure, stabbing)
• Severity on a 0–10 scale
• Associated symptoms (nausea, light sensitivity, aura)
• What you took for it and whether it helped
• Possible triggers (sleep changes, stress, certain foods, menstrual cycle)

This record helps distinguish primary from secondary headache, identify medication overuse patterns, and guide treatment choices 1Ref 1Walling A (2020).Frequent Headaches: Evaluation and Management.Overview of primary vs secondary headache evaluation, when neuroimaging is indicated, medication overuse headache prevalence and management, and the clinical history as the cornerstone of diagnosis.