Quick Answer
Most of the time, lightheadedness means your brain isn't getting enough blood or oxygen for a brief moment.
Common Fix: Sit down, drink water, and eat a small snack. It usually passes quickly.
Top 5 Causes
1. Dehydration
Low fluid volume lowers blood pressure, making it harder for blood to reach your brain.
2. Low Blood Sugar (Hypoglycemia)
Common if you skip meals or have diabetes. You may also feel shaky, sweaty, or irritable.
3. Orthostatic Hypotension
A fancy term for "standing up too fast." Blood rushes to your legs, causing a temporary drop in blood pressure.
4. Medication Side Effects
Blood pressure meds, water pills (diuretics), and some antidepressants common culprits.
5. Heart Issues
Serious (but less common): Arrhythmias (irregular heartbeat) or valve problems can reduce blood flow.
When to Call a Doctor
- • If you actually pass out (faint).
- • If you have chest pain or palpitations.
- • If you have sudden severe headache or trouble speaking (stroke signs).
- • If it happens often without a clear reason.
Medical Review
Reviewed by: Ricardo Hamilton, MD
Last Updated: December 15, 2025
Sources: Mayo Clinic, Cleveland Clinic