Decompression Sickness (The Bends) in Scuba Diving: Symptoms, Causes and Prevention

What decompression sickness is, how it differs from AGE, common symptoms, risk factors, prevention tips, first aid, and when to call DAN. Not medical advice.

Decompression sickness (DCS), often called the bends, happens when inert gas that dissolved in your tissues at depth forms bubbles as pressure drops too quickly during or after ascent. Divers Alert Network (DAN) groups DCS with arterial gas embolism (AGE) under the broader label decompression illness (DCI). Most cases show as joint pain or numbness and tingling, but severe DCS can affect the brain, spinal cord, or lungs and needs urgent care.

This guide explains what DCS is, how it differs from AGE, which symptoms to watch for, what raises risk, how to reduce it, and what to do if something feels wrong after a dive. I checked the DAN, CDC Yellow Book, and related pages linked below in mid-October 2026. This is educational diving-safety information, not medical advice. If you have symptoms after diving, seek emergency care. Do not self-diagnose from a web page.

Emergency: For life-threatening symptoms, contact local EMS or go to the nearest medical facility first. Then call DAN's emergency hotline at +1-919-684-9111 (24 hours a day, 365 days a year; collect calls accepted). That number is listed on DAN's contact page.

Decompression sickness at a glance

What causes decompression sickness

At depth, the nitrogen (or other inert gas) in your breathing mix dissolves into blood and tissues. The longer and deeper you stay, the more gas you take up. On ascent, ambient pressure falls and that gas needs to leave the tissues in an orderly way through the bloodstream and lungs.

If the pressure drop is too steep for the amount of gas you absorbed, bubbles can form in tissues and blood. DAN describes that as inadequate decompression. Bubbles near joints are the usual explanation for classic joint pain ("the bends"). Higher bubble loads can affect the spinal cord and brain (numbness, weakness, coordination problems) or flood venous blood enough to strain the lungs and circulation (DAN decompression illness).

Important nuance from DAN: DCS can follow a profile that violated limits, and it can also happen when you followed accepted tables or computer guidance. Almost any dive profile can result in DCI. That is why "my computer said I was fine" is not a reason to ignore odd symptoms.

DCS vs AGE (and why both matter)

Sources: DAN, CDC Yellow Book 2026.

In the field you often cannot tell DCS from AGE with certainty, and you do not need to. Early management is the same. Rescue training (see our Rescue Diver guide) covers recognizing dive emergencies and using oxygen within the limits of your certification.

Symptoms of decompression sickness

DAN lists joint pain and numbness or tingling as the most common manifestations. Next most common are muscular weakness and difficulty emptying a full bladder. Severe DCS is usually obvious. Mild DCS often looks subtle: a minor joint ache or a strange burning or tingling feeling in a limb that is easy to blame on a tight wetsuit, lifting tanks, or being tired (DAN).

Common and serious signs DAN lists for DCS

• Unusual fatigue
• Skin itch
• Pain in joints or in arm, leg, or torso muscles
• Dizziness or vertigo
• Ringing in the ears
• Numbness, tingling, and/or paralysis
• Shortness of breath
• A blotchy rash
• Muscle weakness or paralysis
• Difficulty urinating
• Confusion, personality changes, or bizarre behavior
• Amnesia
• Tremors
• Staggering
• Coughing up bloody, frothy sputum
• Unconsciousness or collapse

DAN's timing note: signs and symptoms usually appear within 15 minutes or up to 12 hours after surfacing. Severe cases may appear before surfacing or immediately afterward. Delayed onset is rare but can happen, especially if air travel follows diving.

CDC's Yellow Book adds that you should be suspicious of any unusual symptoms soon after a dive, especially neurological ones, and that surface-level 100% oxygen is first aid, not a substitute for evaluation (CDC Yellow Book).

Denial is dangerous. DAN and other dive-medicine educators stress that oxygen can make symptoms improve temporarily and then return. Always contact DAN or a physician trained in dive medicine if you suspect DCI, even when symptoms seem to have gone away.

What increases risk

DAN's known risk factors for divers are:

• Deep or long dives
• Cold water
• Heavy exercise at depth
• Rapid ascents

Rapid ascents also contribute strongly to AGE risk. Factors that may increase DCI risk but lack conclusive evidence (per DAN) include obesity, dehydration, heavy exercise right after surfacing, and pulmonary disease. Individual susceptibility is still poorly understood: some divers get DCI more often than others on the same profile (DAN).

The CDC Yellow Book highlights depth, time, and ascent rate as primary drivers, and lists additional practical stressors: altitude too soon after diving, colder water, currents, poor visibility, wave action, dives deeper than about 18 m / 60 ft, multi-day or repetitive diving, overhead environments (caves, wrecks), strenuous exercise, and dehydration (CDC).

Trip format matters. A week of four-dive days on a liveaboard stacks nitrogen load differently than one easy reef dive. Deeper adventure dives in Advanced Open Water training also push closer to recreational limits. Plan surface intervals and your last-dive-to-flight gap with that load in mind.

How to reduce the risk of decompression sickness

No checklist eliminates DCS. These practices, drawn from DAN and CDC guidance, lower the odds:

1. Dive conservatively. Stay well inside no-decompression limits on tables or computers. DAN says experienced divers sometimes plan a table depth 10 feet (3 meters) deeper than the actual depth, and recommends that habit for all divers in cold water or hard conditions. Be especially cautious about approaching no-decompression limits deeper than 100 feet (30 meters) (DAN).
2. Ascend slowly and breathe normally. Controlled ascent and continuous normal breathing reduce both DCS and AGE risk. Never hold your breath on scuba.
3. Respect multi-dive and multi-day nitrogen. Build in the surface intervals your computer or tables require. Do not "push" a last dive before a flight or a mountain drive.
4. Avoid altitude too soon. See the flying section below. Any ascent to altitude after diving (including by car) increases decompression stress.
5. Stay hydrated and rested. CDC specifically cautions divers to stay well hydrated and rested and to dive within their training (CDC).
6. Get fit to dive. CDC notes that diving is strenuous and that serious injury and death are associated with poor physical conditioning. Resolve new health changes with a physician who understands diving before you travel.
7. Match the dive to your certification. Open Water skills from your PADI Open Water course are the foundation. Deeper profiles, wrecks, and overhead environments need extra training and honest self-assessment.

Flying after diving (and other altitude)

Cabin altitude on commercial flights is often in the 6,000 to 8,000 foot range. That extra pressure drop after diving raises DCS risk. For divers without DCS symptoms, DAN's 2002 workshop consensus (still published on DAN's flying-after-diving page) recommends:

These intervals reduce risk; they do not guarantee you will avoid DCS. Longer waits help more. The guidelines apply to flights at cabin altitudes of about 2,000 to 8,000 feet (610 to 2,438 meters). Do not fly with symptoms. Seek medical advice first (DAN flying after diving; CDC Yellow Book publishes the same 12 / 18 hour framework and notes 24 to 48 hours after dives that required stops).

What to do if you suspect the bends

1. Life threat first. If the diver is unconscious, not breathing, or clearly deteriorating, call local EMS and start CPR if you are trained and it is indicated.
2. Give oxygen. DAN and CDC both emphasize early 100% oxygen first aid when you are trained and equipment is available. Keep giving oxygen until medical professionals take over, even if the diver feels better.
3. Call DAN. After contacting local EMS (or in parallel when symptoms are milder but still concerning), call +1-919-684-9111. DAN medics can help with next steps, chamber location, and transport planning. Collect calls are accepted (DAN contact; also cited in CDC Yellow Book).
4. Get to a medical facility. DAN says divers with AGE or severe DCS need stabilization at the nearest medical facility before chamber transport. Do not attempt in-water recompression unless you are specifically trained and equipped for that protocol; recreational divers should not treat this as DIY.
5. Capture the dive history. Depths, times, ascent issues, gases, surface intervals for the prior 48 hours, symptom onset, and what oxygen or fluids you gave all help clinicians.
6. Do not wait for perfection. DAN notes that after a delay of 24 hours or more, treatment may be less effective. Still call a dive medicine specialist even if you delayed; do not decide on your own that it is "too late."

Definitive treatment is recompression with hyperbaric oxygen under medical supervision. Outcomes are better with prompt care. Residual symptoms can remain after severe cases; follow-up treatments and physical therapy may help (DAN).

Returning to diving after DCI

For recreational divers, DAN's published conservative guidance is:

• Pain-only DCI without neurological symptoms: consider returning after a minimum of two weeks
• Minor neurological symptoms: consider returning after six weeks
• Severe neurological symptoms or any residual symptoms: do not return to diving without specialist clearance

Always consult a physician before diving again. Repeated DCI when buddies on the same profile stay fine is a reason to see a dive medicine specialist about susceptibility (DAN).

FAQ

What is the difference between decompression sickness and decompression illness?

Decompression illness (DCI) is the umbrella term. It includes decompression sickness (DCS, also called the bends) and arterial gas embolism (AGE). DCS comes from inert-gas bubbles forming in tissues after a pressure drop. AGE usually follows lung overexpansion that sends bubbles into arterial blood. Field first aid starts the same way for both: oxygen, stabilize, and get medical help.

How soon after a dive can decompression sickness symptoms appear?

Divers Alert Network says DCS signs and symptoms usually appear within 15 minutes to 12 hours after surfacing. Severe cases can show before surfacing or right afterward. Delayed onset is uncommon but can happen, especially if you fly after diving. The CDC notes that AGE often presents when a diver surfaces unconscious or loses consciousness within about 10 minutes of surfacing.

Can you get the bends even if you stayed within no-decompression limits?

Yes. DAN notes that bubbles and DCS can occur even when you follow accepted guidelines, and that almost any dive profile can result in DCI. Depth, time, ascent rate, cold water, hard work at depth, and individual factors all affect risk. Treat unusual post-dive symptoms seriously even if your computer never went into deco.

What should I do if I suspect decompression sickness?

Call local emergency medical services first for life-threatening symptoms, then call DAN's emergency hotline at +1-919-684-9111 (24/7; collect calls accepted). Give 100% oxygen if you are trained and it is available. Do not skip medical evaluation just because symptoms improve on oxygen. DAN says symptoms can resolve temporarily and then return.

How long should I wait to fly after diving?

For divers with no DCS symptoms, DAN's consensus guidelines recommend a minimum of 12 hours after a single no-decompression dive and 18 hours after multiple dives in a day or multiple days of diving. After dives that required decompression stops, wait substantially longer than 18 hours. Longer surface intervals further reduce risk. Do not fly with symptoms until a dive medicine clinician clears you.

When can I return to diving after decompression sickness?

DAN's recreational guidance is conservative: consider at least two weeks after pain-only DCI without neurological symptoms, and at least six weeks after minor neurological symptoms. If you had severe neurological symptoms or any residual symptoms, DAN says you should not return to diving without specialist advice. Always see a physician trained in dive medicine before you dive again.

Does nitrox prevent decompression sickness?

Enriched air (nitrox) can give you longer no-decompression times or shorter surface intervals for a given profile when you use it correctly with a matching computer or tables. It does not make you immune to DCS. You still need a controlled ascent, conservative margins, and the usual surface-interval rules before flying. Training agencies teach nitrox as a tool, not a guarantee.

Key takeaways

• Decompression sickness is bubble injury from inert gas after a pressure drop; it sits under DCI alongside AGE.
• Joint pain and numbness/tingling are common; neurological or breathing problems are emergencies.
• You can get DCS even inside no-decompression limits. Timing is often 15 minutes to 12 hours after surfacing.
• Prevention: conservative profiles, slow ascents, hydration, rest, and DAN's 12 / 18 hour (or longer) flying waits.
• Suspect DCI? Local EMS if needed, 100% oxygen if trained, call DAN at +1-919-684-9111, get medical evaluation even if symptoms fade.

Next steps

Keep building the skills that prevent and manage emergencies: finish Open Water fundamentals if you are new, add depth and navigation through Advanced Open Water, and take Rescue Diver so oxygen use and emergency management are practiced, not theoretical. If you are planning a multi-day boat trip, read our liveaboard diving guide with nitrogen load and flight timing in mind.

Save DAN's number in your phone before your next trip: +1-919-684-9111.

If you run a dive shop and want a clearer site for courses, safety briefings, and bookings, ScubaDock builds dive shop websites at /for-dive-shops.

References

• Divers Alert Network. Decompression Illness. Checked October 2026.
• Divers Alert Network. Contact Us (Emergency Hotline). Checked October 2026.
• Divers Alert Network. Flying After Diving. Checked October 2026.
• CDC Yellow Book 2026. Scuba Diving: Decompression Illness and Other Dive-Related Injuries. Updated April 23, 2025; checked October 2026.

Disclaimer: ScubaDock is not a medical provider. This article summarizes publicly available dive-safety guidance for education only. It is not a diagnosis, treatment plan, or substitute for emergency care or advice from a physician trained in dive medicine.