How Long to Wait After Diving Before Going to High Altitude

How Long to Wait After Diving Before Going to High Altitude

Wait 12–24 hours between diving and high altitude above 2400m elevation. If you're going to altitudes between 1800–2400m, wait at least overnight. Below 1800m sea level equivalent, you're generally safe within a few hours — but overnight is always safer.

Why? When you dive, nitrogen dissolves into your body tissues. At sea level, your body off-gasses that nitrogen slowly and safely. At altitude, the lower air pressure forces your body to decompress faster. If you've still got nitrogen in your system from diving, that rapid decompression can cause nitrogen bubbles to form in your tissues — that's decompression sickness (the bends), and it's a serious medical emergency even after shallow dives.

Most new divers don't know this rule because theory overload makes it easy to miss. And some instructors don't volunteer the information unless you ask. If your instructor suggests a post-dive hike to high altitude without mentioning decompression risk, that's a red flag about their safety culture.

The safe approach: Dive, wait overnight, then hike. Or hike first, then dive the next day.

Why Altitude Compounds Decompression Risk

During a dive, nitrogen molecules from your breathing air dissolve into your bloodstream and tissues. Your body off-gasses (eliminates) that nitrogen gradually, mostly through breathing at the surface. This takes time — that's why dive tables and computers track no-decompression limits.

At sea level, the air pressure is about 1 atmosphere (bar). Your body off-gasses nitrogen smoothly because the pressure gradient is gentle. At 1800m elevation, the air pressure drops to roughly 0.8 bar. At 2300m, it's about 0.75 bar. At 3500m (many high-altitude hiking destinations), it's down to 0.6 bar.

That steep pressure drop forces your body to decompress too fast. Any nitrogen still dissolved in your blood and tissues can form bubbles — especially in joints, the spine, and the nervous system. Even a dive to 18 meters (60 feet) on open water certification can leave residual nitrogen for 12–24 hours afterward.

Decompression sickness can strike hours after you reach altitude. Symptoms include joint pain ("the bends"), numbness, tingling, dizziness, difficulty breathing, or even paralysis in severe cases. Treatment requires recompression in a hyperbaric chamber, which isn't something you want to search for in a remote mountain village.

The 12–24 Hour Rule (And Why It Exists)