Quick Answer
The seven most common causes of headaches after running are dehydration, primary exertion headache, low blood sugar, overheating, electrolyte imbalance, tension from poor posture, and sun or glare exposure. Most resolve within 30–60 minutes by rehydrating, eating a small snack, and resting in a cool environment. Seek medical attention if the headache is sudden and severe, is the worst of your life, or comes with vomiting, vision changes, confusion, or neck stiffness — these can signal a secondary exercise headache caused by a serious underlying condition.
Primary vs Secondary Exercise Headaches: The Key Distinction
Medical providers classify exercise headaches into two categories, and the distinction matters.
Primary exercise headaches occur on their own — they’re not caused by any underlying condition. They typically feel like a throbbing, pulsating pain on both sides of the head, come on during or shortly after exertion, and last anywhere from 5 minutes to 48 hours. They’re generally harmless and often resolve on their own within a few months. They’re more common in hot weather and at altitude, and a proper warm-up can reduce their frequency.
Secondary exercise headaches are caused by an underlying problem — which may involve the brain or cardiovascular system. They tend to last longer (more than 24 hours), may come with other symptoms like nausea, vomiting, visual disturbance, or neck stiffness, and require medical evaluation. If you have any doubt about which type you’re experiencing, see a doctor.
7 Causes of Headache After Running: At a Glance
👉 Swipe to view full table
| Cause | Typical symptoms | When it occurs | Immediate fix | Prevention |
|---|---|---|---|---|
| Dehydration | Dull, generalised ache; dry mouth; dark urine | During or after run | 500ml water or electrolyte drink | Hydrate throughout the day; sip during runs over 30 min |
| Primary exertion headache | Throbbing, both sides of head; no other symptoms | During or just after hard effort | Rest; ibuprofen if needed | Gradual warm-up; avoid maximal efforts in heat |
| Low blood sugar (hypoglycaemia) | Headache + dizziness, shakiness, fatigue | After fasted runs or long efforts | Fast carbohydrate snack (banana, sports drink) | Eat before runs over 60 min; carry a gel on long runs |
| Overheating / heat exhaustion | Throbbing headache + flushed skin, nausea, dizziness | After hot-weather runs | Cool environment; cold wet cloth on neck; rehydrate | Run in cooler conditions; wear light-coloured clothing; reduce intensity in heat |
| Electrolyte imbalance | Headache + muscle cramps, nausea | After long sweaty runs | Electrolyte drink (sodium, potassium) | Use electrolytes on runs over 60–90 min or in heat |
| Tension / neck and shoulder tightness | Dull ache at back of head or temples; neck stiffness | After run; worsens later in day | Gentle neck and shoulder stretching; heat pack | Improve running posture; relax shoulders; use a supportive pillow |
| Sun and glare exposure | Frontal or generalised headache; eye strain | After outdoor runs in bright conditions | Move to shade; cool compress over eyes | Wear sunglasses and a cap; avoid peak sun hours (10am–3pm) |
If you are not yet running at all, start with a Couch to 5K program first. Building a base of running 3–5 km comfortably before entering a half marathon plan significantly reduces injury risk and improves the quality of every training week.
Cause-by-Cause Breakdown
1. Dehydration
Dehydration is the single most common cause of post-run headaches. When you sweat, you lose fluid that supports blood volume and oxygen delivery. As little as 1–2% loss of body weight through sweat — roughly 700ml–1.4 litres for a 70 kg runner — is enough to trigger a noticeable headache in many people. The brain is particularly sensitive to fluid shifts; as blood volume drops, the brain can temporarily shrink slightly within the skull, stretching pain-sensitive structures.
The fix is straightforward: drink 400–600ml of water in the hour before running, sip 150–200ml every 20 minutes on runs longer than 30 minutes, and rehydrate with 500ml after finishing. Dark urine after a run is a reliable sign you went into the run already under-hydrated. For a detailed guide to running hydration strategy, see our article on endurance hydration.
2. Primary Exertion Headache
A primary exertion headache is triggered by intense physical effort — the blood vessels supplying the brain dilate rapidly under increased demand, causing a throbbing, bilateral pressure that can range from uncomfortable to debilitating. It is more common in people who run in hot or humid conditions, at altitude, or who go from rest to hard effort without a gradual warm-up.
Most primary exertion headaches resolve within a few hours with rest and over-the-counter anti-inflammatories such as ibuprofen. Importantly, they tend to stop occurring on their own within 3–6 months for most people. A consistent warm-up of at least 10 minutes of easy running before hard efforts is the most effective preventive measure. If they are frequent and severe, a doctor can prescribe preventive medications such as indomethacin or beta-blockers.
3. Low Blood Sugar
Running on an empty stomach or finishing a long run without adequate fuelling can deplete blood glucose to a level that triggers a headache, often accompanied by dizziness, shakiness, or a sudden drop in energy. The brain depends almost entirely on glucose for fuel, so even a modest drop in blood sugar has a rapid and noticeable effect.
For runs under 60 minutes, most people have adequate glycogen stores and don’t need to eat beforehand. For longer runs, a small carbohydrate-based snack 60–90 minutes before starting — a banana, toast with honey, or a small bowl of oats — significantly reduces the risk. On runs longer than 75–90 minutes, carrying a gel or sports drink provides a mid-run glucose boost that prevents this entirely. See our guide on what to eat before a run for specific fuelling recommendations by distance.
4. Overheating
Running in hot conditions significantly raises core body temperature. When the body’s cooling mechanisms — primarily sweating and skin blood flow — are overwhelmed, core temperature can rise to the point where blood vessel dilation in the head triggers a throbbing headache, often accompanied by nausea, flushed skin, and dizziness. In more serious cases this can progress to heat exhaustion, which requires immediate cooling and medical attention.
If you develop a headache after a hot-weather run, move immediately to a cool environment, apply a cold wet cloth to the neck and forehead, and rehydrate slowly. Avoid resuming exercise until fully recovered. Prevention involves scheduling runs for early morning or evening in summer, wearing light-coloured breathable clothing, reducing intensity on hot days, and ensuring full hydration before you start. Running in cooler conditions or cross-training on extreme heat days is often the smarter call.
5. Electrolyte Imbalance
During long runs or hard sessions in heat, you lose not just water but electrolytes — primarily sodium, and to a lesser degree potassium, magnesium, and calcium — through sweat. Replacing lost fluid with plain water without replacing electrolytes can dilute the sodium concentration in the blood (a condition called hyponatraemia), which causes headache, nausea, and in severe cases confusion. Electrolyte loss can also trigger headaches through impaired nerve and muscle function.
On runs longer than 60–90 minutes, especially in warm conditions, using an electrolyte drink or carrying salt tablets is more effective than water alone. Research on salt tablets for runners covers when and how to use them effectively. After a long sweaty run, a salty snack alongside your rehydration drink helps restore sodium faster than water alone.
6. Tension from Poor Posture
Many runners carry significant tension in the neck and shoulders during a run — shoulders hunched, head jutting forward, jaw clenched — particularly when fatigued or running at effort. This sustained muscle tension can trigger tension headaches that radiate from the base of the skull up across the head and into the temples. They typically feel like a dull, tight band of pressure rather than a throbbing pulse, and often worsen in the hours after a run.
During runs, make a conscious effort to drop your shoulders away from your ears, keep your gaze forward rather than down, and relax your hands. A quick posture check every 5–10 minutes during longer runs reinforces good habits. After running, gentle neck stretches — slowly tilting the ear toward each shoulder and rotating the head slowly side to side — combined with a heat pack on the upper traps can relieve tension quickly.
7. Sun and Glare Exposure
Squinting against bright sunlight, glare off roads or water, or running without eye protection during high UV periods creates sustained strain in the muscles around the eyes and forehead. This can trigger a frontal headache that develops during or after an outdoor run, particularly in Australian summer conditions. The UV intensity in Australia between October and March makes eye protection a practical necessity, not a luxury.
Wearing UV-protective sunglasses and a cap or visor for any outdoor run between 9am and 4pm reduces this risk significantly. Avoiding peak sun hours — typically 10am to 3pm during summer — reduces both glare-related headache risk and heat exposure simultaneously.
When to See a Doctor: Red Flag Symptoms
Most post-run headaches are benign and resolve quickly with the simple measures above. However, you should seek medical attention promptly — same day — if your headache has any of the following features:
Thunderclap onset. A headache that reaches maximum intensity within seconds of starting, described as “the worst headache of your life,” is a medical emergency. It can indicate subarachnoid haemorrhage and requires immediate assessment.
Neurological symptoms. Headache accompanied by vision changes, confusion, weakness or numbness in the limbs, speech difficulty, or loss of coordination requires urgent evaluation to rule out neurological causes.
Neck stiffness or sensitivity to light. Combined with a headache, these can indicate meningitis — a medical emergency.
Headache lasting more than 48 hours. Primary exertion headaches resolve within 48 hours. One that persists beyond this, or keeps worsening after you stop running, should be investigated.
New onset headaches after months of pain-free running. If you have been running regularly without headache issues and one develops suddenly, see a doctor to rule out a secondary cause.
Prevention Checklist: Stop Post-Run Headaches Before They Start
Hydration. Drink consistently throughout the day — not just before runs. Aim for pale yellow urine as your baseline hydration marker. Use electrolyte drinks on runs over 60 minutes or in hot conditions.
Fuel properly. Don’t run long efforts fasted. A small carbohydrate snack before runs over 60 minutes and an in-run fuel source for anything over 75–90 minutes keeps blood sugar stable.
Warm up. Ten minutes of easy running before any hard effort significantly reduces the risk of primary exertion headaches by allowing a gradual increase in cerebral blood flow rather than a sudden spike.
Manage heat exposure. Schedule hard sessions for cooler times of day. Reduce intensity in heat. Cover up and wear sunglasses. Know that your body’s heat tolerance takes 10–14 days to adapt when moving into warmer weather — reduce intensity during that adjustment window.
Check your posture. Conscious shoulder relaxation, a forward gaze, and a relaxed jaw reduce neck and shoulder tension. A strength programme for runners that includes upper back and neck strengthening improves postural endurance on longer runs.
If headaches persist despite addressing all the above factors, keep a brief training log noting conditions, duration, intensity, hydration, and food. Patterns usually emerge within 2–3 weeks that point clearly to the cause. If they don’t, a sports medicine doctor or GP can help investigate further. For other symptoms runners sometimes experience post-run, our guides on dizziness after running and nausea after running cover related causes and fixes in detail.
Run Smarter, Feel Better
A structured training plan with the right pacing, recovery, and fuelling guidance reduces the chance of post-run symptoms — and helps you train consistently without setbacks.
Get Running Coaching → Browse Training Plans →
FAQ: Headache After Running
Why do I get a headache after running?
The most common causes are dehydration, primary exertion headache, low blood sugar, overheating, electrolyte imbalance, tension from poor posture, and sun exposure. Most are simple to fix once you identify which type you’re dealing with.
How do I get rid of a headache after running?
Rehydrate with 500ml of water or an electrolyte drink, eat a small carbohydrate snack if you haven’t eaten, rest in a cool environment, and take ibuprofen if the headache is from exertion. Most running headaches resolve within 30–60 minutes.
What is a primary exercise headache?
A throbbing, bilateral headache triggered directly by physical exertion with no underlying cause. It lasts between 5 minutes and 48 hours, is more common in heat and at altitude, and usually resolves on its own over several months. A proper warm-up before hard efforts is the best prevention.
When should I see a doctor about a headache after running?
Seek same-day medical attention for a thunderclap-onset headache, the worst headache of your life, or any headache accompanied by vomiting, vision changes, confusion, neck stiffness, or neurological symptoms. These can indicate a secondary exercise headache caused by a serious underlying condition.
Can dehydration cause headaches after running?
Yes — it’s the most common cause. Even losing 1–2% of body weight through sweat can trigger a dehydration headache. The fix is consistent hydration before, during, and after runs, with electrolytes added on longer or hotter sessions.
Find Your Next Running Race
Ready to put your training to the test? Here are some upcoming running events matched to this article.
