If you’ve ever felt dizzy, lightheaded, or like your head is spinning, congratulations: You’re a normal human being. We used to spin because dizziness seemed fun (ah, the good ol’ days), but not so much once adulthood rolled around.

There are so many things that could make you dizzy–like medications and dehydration—and most of them are minor and nothing to worry about, Catherine Cho, M.D., clinical associate professor in the departments of neurology and otolaryngology at NYU Langone Medical Center, tells SELF.

In some situations, though, dizziness can be a sign of something more serious. Here is how to tell the difference between a minor spell of the spins and when it’s time to consult a neurologist to figure out what’s making you so faint.

1. Your dizzy spells are frequent or last longer than a few minutes.

A common condition called vertigo causes an “illusion of movement,” Cho explains. It’s caused by a disconnect between your ears and your brain, which results in a spinning sensation. Brief episodes can be triggered, most commonly, by rapid change in head movement, according to the Mayo Clinic. In most cases, especially in younger patients, the condition will resolve on its own, Cho says. But if you have it constantly, episodes that last hours at a time, or it’s accompanied by ringing in the ears or hearing loss, it could be a sign of a more serious ear disorder or undiagnosed migraines.

2. You’re also experiencing symptoms like numbness, weakness, speech problems, clumsiness, or vision problems.

Vertigo can actually be a sign of a stroke. If you feel a spinning-dizzy sensation that hits suddenly and also experience any other symptoms of stroke at the same time (for instance, weakness especially on one side of the body, sudden severe headache, or trouble speaking, seeing, or walking), you should see a doctor to rule it out. Cho urges a visit to the emergency room where doctors can do a quick check to make sure. Some other neurological conditions (like multiple sclerosis) can cause similar symptoms—they may not be as life-threatening, but it’s important to get them diagnosed so you can treat them.

3. You feel dizzy when you stand up.

Orthostatic hypotension—low blood pressure that happens when you stand up—can make you feel faint, but is usually nothing to worry about. The most likely cause is dehydration. “Especially in the summer months, people forget to drink more. You don’t have to be dripping sweat to become dehydrated,” Cho says. If loading up on H2O doesn’t stop these dizzy spells, there are some other disorders that could be causing low blood pressure or poor circulation, leading to dizziness. Cardiovascular disease (arrhythmias or congestive heart failure), and conditions that are most typical in diabetics—such as neuropathy (nerve damage) or hypoglycemia (low blood sugar)—can all cause this dizzy or lightheaded sensation.

4. You have a history of migraines.

If your dizziness feels like your head is spinning (not the room), it could mean you’re suffering from migraines without knowing it, Cho says. Some people don’t realize their headaches are actually migraines if they don’t also see flashing lights or auras—but those symptoms are not always necessary.

5. You recently hit your head.

Cho says that you can also experience dizzy spells after getting a concussion. If you hit your head and never got it checked out, but sometimes feel like your head gets a little spinny, there’s a chance that bump did more than you thought.

6. You get dizzy during your workouts.

In this case, dehydration is the most likely culprit. It may not seem like a big deal, but if you’re constantly feeling this way during physical activity, focus on hydrating more to see if the problem stops; getting dizzy in the gym or out on a run is a good way to fall and injure yourself. Though not as common, exercise so intense that you’re gasping for air can cause hyperventilation, rapid breathing that causes carbon dioxide levels in the blood to drop, resulting in lightheadedness.

Bottom line: If a dizzy spell is so bad you can’t function, it’s worth seeing a doctor, even if it only happens once. As for those times every now and then that you get dizzy or lightheaded and it goes away? Stop worrying, and take a few slugs from your water bottle instead.