A blog by runners. For runners.

Why am I dizzy during – or after – a run?

Why do I feel dizzy after and during a run?Feeling dizzy during or after a run can be a frightening experience. Maybe you just felt a little woozy or perhaps you even fainted. No matter how severe your symptoms are, dizziness is not something you want to mess around with.

Causes of dizziness

Dizziness during and immediately following a run can happen for a few reasons. 

  • Dehydration: Not taking in enough liquids could lead to a host of unpleasant symptoms, including dizziness. If you’re dehydrated to the point of feeling dizzy, the Mayo Clinic suggests you seek medical help right away. Prevent dehydration by drinking plenty of fluids throughout the day and during your run. Follow these hydration guidelines.
  • Heat exhaustion. Dizziness can be a warning sign of heat exhaustion. If you’ll be running in the heat, follow these tips to stay safe and comfortable.
  • Low blood sugar. If you don’t adequately fuel for your workout, your blood sugar levels will plummet. This can cause you to feel dizzy, lightheaded, and weak. Eating well before and during a run is crucial for keeping your blood sugar levels stable. This is true even if you’re an early morning runner – it’s a good idea to eat a light snack before heading out the door.
  • Low blood pressure. Low blood pressure can cause dizziness. But even if you don’t typically have low blood pressure, running can cause your blood pressure to drop. During exercise, blood flow increases to the muscles we’re using – the legs. Once you stop moving, it can take some time for the blood to flow back to your brain. Less blood flow to the brain can cause you to feel dizzy and even collapse. This is called “exercise-associated postural hypotension” and it’s the reason why you might see runners collapse right after finishing a race. Lying down on the ground with your legs elevated against a wall or fence can help remedy this problem.
  • Underlying health issues. Sometimes dizziness can be a sign of a more serious health problem, such as exercise-induced asthma or an abnormal heart rhythm (arrhythmia). In these conditions, you may only feel dizzy during periods of physical activity. This is why it’s a good idea to visit a doctor if you feel dizzy during or after a run. Even if you think your lightheadedness stemmed from something as simple as not eating enough beforehand, head to your doctor just to be sure. Your doctor will be able to tell if your dizziness is due to a minor or major health problem, which could give you peace of mind.

If you feel lightheaded mid-run, stop right away, lie down, and put your legs up. If that doesn’t relieve your symptoms, seek medical help. Whatever you do, don’t continue your run just because you “need” to finish your workout – it’s not worth the risk.

Written by Jen Matz.