Headache After Running: 7 Causes and How to Fix Each One

You finish a run, sit down, and a dull ache builds behind your eyes or at the back of your head. It is common, and most of the time the cause is simple: you finished short on fluid, salt, or sugar, or you ran hot, tense, or off your normal caffeine routine. Those are fueling and hydration problems, which means they are fixable.

This guide covers the seven most common causes, how to tell them apart, what to do in the next 30 minutes, and how to stop the next headache before it starts. It also lists the warning signs that mean a headache is not about fueling at all.

Quick Answer: Which Cause Is Yours?

1. Dehydration

This is the most common cause. You lose fluid with sweat, often half a liter to one and a half liters per hour and more in the heat, and most runners replace only part of it. For people who are prone to it, a small fluid deficit is enough to bring on a headache. In one survey, about one in ten people said they get a headache when they go without water, and most of them felt better within 30 minutes of drinking about half a liter.

Signs: dark urine, thirst, a dry mouth, a headache that gets worse when you bend down or walk, and a big drop on the scale after the run. Weighing yourself before and after a run tells you how much you lost. Each kilogram lost is about a liter of fluid.

• Fix it now: drink 500 ml of water or sports drink over 30 minutes and eat a salty snack. Over the next few hours, replace about 1.25 to 1.5 liters for every kilogram you lost.
• Prevent it: start runs with pale urine, and on runs longer than an hour, drink to a plan based on your sweat rate. You do not need to replace every drop. Losing up to about 2 percent of body weight during a run is normal.

2. Low Blood Sugar

If you ran before breakfast, ran long without eating, or have been eating less than usual, your blood sugar can drop during or after the run. The headache often comes with shakiness, sweating, hunger, irritability, or a weak, foggy feeling. Long runs are the usual trigger because they use up the liver glycogen that keeps blood sugar steady.

• Fix it now: eat 20 to 30 g of fast carbohydrate, such as a banana, a glass of juice, a gel, or a handful of sweets. Follow it within an hour with a real meal that has carbs and protein.
• Prevent it: eat something with carbs before runs longer than an hour. On runs over 75 to 90 minutes, take 30 to 60 g of carbohydrate per hour. If you like fasted running, keep it to short, easy runs.

3. Salt Loss

Sweat contains salt, and some runners lose a lot of it. If you see white salt marks on your cap, shirt, or face after a run, you are probably one of them. Replacing heavy sweat losses with plain water alone can leave your blood sodium low, which brings headache, nausea, and fatigue. In rare cases, drinking far more than you sweat during a long event causes dangerously low blood sodium, called hyponatremia.

• Fix it now: eat something salty, such as pretzels, broth, or salted crackers, or drink an electrolyte drink. Do not force more plain water.
• Prevent it: on long or hot runs, use an electrolyte drink or salt tablets and drink to thirst or to your measured sweat rate, not as much as possible.
• Warning: if you feel bloated, confused, or very sick, or your hands and feet are swollen after drinking a lot during a long run, get medical help. Do not drink more water.

4. Heat and Sun

Running in the heat raises your core temperature and makes you sweat more, so dehydration and salt loss stack up faster. Bright sun and glare add squinting and tension. A heat headache often feels like pressure at the temples or forehead and comes with a flushed face and a wiped-out feeling.

• Fix it now: get into shade or air conditioning, cool your neck and face with cold water, drink cold fluids with some salt, and rest.
• Prevent it: run early or late, slow down on hot days, wear a light cap and sunglasses, and carry fluid on runs over 45 minutes.
• Warning: confusion, stopping sweating, vomiting, or feeling very hot and dizzy are signs of heat illness. Stop and get help.

5. Caffeine Timing

If you drink coffee every day and run before your first cup, or skip it, the headache may be caffeine withdrawal. Headache is the most common withdrawal symptom. It usually starts 12 to 24 hours after the last dose and can appear after stopping as little as 100 mg a day, about one cup of coffee.

• Fix it now: have your normal coffee.
• Prevent it: keep your caffeine routine steady. Have your usual cup before morning runs, and do not cut caffeine suddenly in race week. Too much caffeine can also cause headaches, so do not stack a big coffee with caffeinated gels you have not tested.

6. Tension and Posture

Running with tight shoulders, a pushed-forward chin, or a clenched jaw loads the muscles of the neck and upper back. A tight cap, headband, or ponytail pulls on the scalp. The result is a pressing, band-like headache, often at the back of the head or across the forehead. It is common late in hard runs, when form falls apart.

• Fix it now: gentle neck and shoulder stretches, a warm shower or heat pack, and loosening whatever was tight.
• Prevent it: check your form halfway through runs: shoulders down, hands loose, jaw relaxed. Loosen your cap or ponytail.

7. Exercise Headache and Migraine

Some headaches are not about fuel. Primary exercise headache is a throbbing headache that starts during or after hard exercise and can last from a few minutes up to 48 hours. It is more common than most people think: surveys of the general population find it in about 1 in 20 adults, often starting in their late twenties. Hot weather and high altitude make it more likely.

If you have migraine, running can trigger an attack. In a clinic study of migraine patients, 38 percent said exercise had triggered an attack at some point. Missing meals and not drinking enough are common migraine triggers too, so the fueling fixes above help here as well. Doctors want to check the first exercise headache to rule out other causes. After that, a longer warm-up, a gradual build in intensity, and sometimes medication before exercise can help.

When to See a Doctor

Most headaches after running are harmless. Get urgent medical help if you have any of these:

• A sudden, severe headache that peaks within a minute, the worst you have ever had.
• Headache with confusion, fainting, trouble speaking, weakness, numbness, or vision loss.
• Headache with a stiff neck, fever, or a rash.
• Headache with vomiting, swelling, or confusion after drinking a lot of fluid during a long event.
• Headache with chest pain or shortness of breath.

See your doctor soon if this is the first time you have had a strong, throbbing headache with exercise, if the pattern is new and you are over 40, or if headaches after running last more than a day.

A Simple Prevention Routine

Runners who get regular headaches after running are usually short on the same thing every time. The pattern is the clue. Note the run length, the weather, what you ate and drank, and when the headache came. After three or four runs, the cause usually stands out.

Mavr reads your runs from Garmin, Strava, or Apple Health and tells you how much to drink, how much sodium, and how many carbs to take for each one, including long runs and hot days.

Plan Fluids, Salt, and Carbs for Every Run

Frequently Asked Questions

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