Can You Scuba Dive With Diabetes? Insulin, Glucose Checks and Rules

Can you scuba dive with diabetes?

Yes, if you meet the medical criteria and follow a set routine on dive days. For years the diving medicine community treated insulin-treated diabetes as an absolute contraindication. The UK reversed its ban in 1991, and in June 2005 a workshop run by the Undersea and Hyperbaric Medical Society (UHMS) and Divers Alert Network (DAN) agreed consensus guidelines for recreational diving with diabetes. DAN stresses that they are guidelines, not rules, and that not everyone with diabetes who wants to dive will qualify.

The physician guidance that goes with the international diver medical form still lists hypoglycaemia in people on insulin or certain oral drugs as a severe risk, so diving is generally contraindicated unless it follows those consensus guidelines. On the 2026 form, diabetes comes up in question 8, and a yes means a medical evaluation before training. Our diver medical questionnaire guide explains how the form works.

This is general information, not medical advice. The guidelines do not clear you to dive: a physician does, ideally one trained in diving medicine working with your own diabetes team. DAN's Medical Information Line (+1 919 684 2948, option 4, Monday to Friday 8:30 a.m. to 5 p.m. US Eastern time) answers fitness-to-dive questions. More health topics are in our safety guides.

Why is low blood sugar the main risk underwater?

Because a bad hypo can take away consciousness, and underwater that can mean drowning. SPUMS, the Australian and New Zealand diving medicine society, says a hypoglycaemic episode with blood glucose below 4 mmol/L (72 mg/dL) carries a risk of confusion, seizures and death. DAN adds that a seizure or blackout is likely to be fatal underwater, that a diver cannot simply stop and rest as on land, and that the buddy system assumes both divers are able to help each other.

UKDMC doctors explain how it happens. Too much insulin can cause a hypo quickly; sulphonylurea tablets such as gliclazide and glibenclamide do it more slowly. Hard finning against a current, fast breathing from anxiety and cold can all bring it on sooner, and a diver in a hypo may lose control of the regulator.

It is also easy to misread. SPUMS notes that confusion and slowed responses can be mistaken for nitrogen narcosis, oxygen toxicity or decompression illness, and that warning signs such as sweating and a fast heart rate may be masked underwater. The 2020 review by Jendle, Adolfsson and Pollock adds fatigue from effort and lethargy from cold, and warns that a wrong call delays the right treatment: carbohydrate, glucagon or hyperbaric oxygen. DAN lists hypothermia and seasickness as other look-alikes; our decompression sickness guide covers the symptoms that can overlap.

Running high is not a free safety margin either. DAN's researchers note that high plasma glucose may increase susceptibility to decompression sickness or worsen neurological decompression illness, so raising glucose to avoid a hypo may not be completely harmless.

Type 1, type 2 on insulin and type 2 on tablets: does the type matter?

The treatment matters more than the label. SPUMS says everyone with type 1 diabetes, and everyone with type 2 who takes insulin, is at risk of a hypo while diving. With type 2 on tablets, the risk depends on the drug.

The UKDMC article says every type 2 treatment except diet alone, or diet plus metformin alone, can cause low blood sugar, and that a diver on diet or metformin alone does not need emergency glucose in the dive kit. The 2020 review grades the newer drug classes as low risk for hypoglycaemia, as the table shows.

Sulphonylureas need the most care. The Australian Diabetes Society (ADS) recommends that people with insulin-requiring type 2 diabetes who also take a sulphonylurea leave it out on dive days. The European EDTC standard notes that people on oral drugs who become hypoglycaemic may be harder to manage than people on insulin. A low hypo risk does not mean a free pass: SPUMS warns that divers who do not need insulin can still have end-organ damage that rules diving out.

Who can be cleared to dive, and what rules it out?

All the main guidelines grew out of the 2005 criteria, then changed a few numbers. All exclude significant complications, with background retinopathy the one exception UKDMC, SPUMS and the ADS name. The UHMS/DAN, SPUMS and ADS criteria also exclude hypoglycaemia unawareness, meaning significant hypos the person does not notice. A Swedish-led review proposes a stricter HbA1c, below 63 mmol/mol (8%).

The complications matter because of what they do in the water. SPUMS points out that coronary artery disease is the leading cause of death among diving fatalities, and diabetes raises its risk. UKDMC doctors add that chest pain on exercise, a possible warning of a heart attack, is often absent in people with diabetes, and that damage to the nerves controlling the heart can stop the heart rate responding normally to exercise or a Valsalva manoeuvre. Numbness and tingling from nerve damage in the limbs can be confused with decompression illness, which makes diagnosis in a chamber harder.

Clearance is not permanent. Each of these guidelines asks for a yearly review, because diabetes can progress.

Blood glucose checks before a dive: 60, 30 and 0 minutes

Test three times in the hour before the dive, and go in only if the level is high enough and not falling. The 2005 guidelines set the checks at 60 minutes, 30 minutes and immediately before diving, with a minimum of 150 mg/dL (8.3 mmol/L), stable or rising. They say to delay the dive below 150 mg/dL or above 300 mg/dL (16.7 mmol/L), and that changing the insulin or tablet dose the evening before or on the day may help.

The other guidelines move the numbers. SPUMS reproduces DAN's protocol with a floor of 8 mmol/L and postpones the dive if any reading is lower than the one before. The ADS adds carbohydrate amounts and a ketone check when glucose is high. The 2020 review accepts a lower floor of 7 mmol/L and suggests 15-30 g of carbohydrate per 70 kg of body weight just before the dive, with no insulin. UK guidance gives no figure beyond a slightly high level. Your own targets should come from your doctor.

What to do if blood sugar drops underwater

Signal, surface with your buddy, then take glucose. That is the order in the 2005 guidelines: the diver surfaces with the buddy, establishes positive buoyancy, takes glucose and leaves the water. The recommended signal for a suspected hypo is an 'L' made with the thumb and index finger of either hand. SPUMS and the ADS use the same sign, and the 2020 review says it can ask a question or give a warning.

Taking glucose underwater is a trained skill, not the default. The UKDMC article describes a tube of glucose paste squeezed into the corner of the mouth without removing the regulator, and says divers must practise it. The ADS allows paste underwater for trained divers but says ascending comes first. Jendle and colleagues suggest practising gel at the surface, then underwater, and want a high level of comfort with it before any dive without direct access to the surface. In the UK survey of 1991-2001, 98% of insulin-treated divers carried glucose paste underwater, and the one reported underwater hypo was treated with paste while submerged.

Backup stays at the surface. DAN strongly recommends injectable glucagon on the boat or shore, with the buddy or someone else trained to give it. The 2020 review says both the diver and the buddy should carry carbohydrate on every dive. The 2005 guidelines, SPUMS, the ADS and UKDMC all ask for an informed buddy who does not have diabetes. Agree the signal and where the gel is kept during your buddy check.

Can you dive with a CGM or insulin pump?

You can wear some sensors in the water, but none is rated for scuba depths, and none has proved accurate enough on dives to replace a finger-prick test. The manufacturer ratings in the table are shallow, and Dexcom says you may not receive readings or alerts while underwater.

Pumps need to come off. Jendle and colleagues say pumps are water-resistant only to about 2.5-3.5 m for short periods, and should be disconnected before the dive and reconnected as soon as possible afterwards. The 2016 ADS statement says to remove both the CGM and the pump before diving.

The studies so far are small. In a 2024 study of 13 divers with type 1 diabetes over 202 dives, the mean error against finger-prick readings (MARD) was 31% for the Dexcom G7 and 14.2% for the FreeStyle Libre 3, and neither was accurate enough to replace finger-pricks. With daily calibration, a 2025 follow-up in 8 divers brought the G7 to 13.7% over 68 dives, but it still missed the US FDA criteria for use without finger-pricks. A 2025 commentary notes that none of these studies tested CGM alarms during dives.

CGM helps most before the trip. The 2020 review recommends at least two weeks of CGM monitoring before diving to catch unexpected swings, and checking the readings with a meter before and after each dive.

What do studies of divers with diabetes show?

Few serious problems in selected, well-controlled divers who follow a protocol, but the groups are small and self-selected. Glucose usually falls during a dive, by very different amounts. In DAN's study, changes ran between a rise of 283 mg/dL and a fall of 370 mg/dL. The ADS review reports a 15-20% drop in daily insulin needs over six days of diving in one study, and a chamber study that found no difference in glucose changes between exercise at sea level and at a simulated 27 m.

DAN notes that its dives were in benign tropical or subtropical water, and harsher conditions or emergencies could cause bigger swings. SPUMS calls the extra risk for a well-selected diver likely to be relatively small, but says it has not been quantified.

Day-of-dive checklist for divers with diabetes

Plan the dive inside the limits first. The 2005 guidelines say to avoid depths beyond 30 m (100 ft), dives longer than 60 minutes, compulsory decompression stops, overhead environments such as caves or wreck penetration, and long cold or hard dives that may bring on a hypo. SPUMS and the ADS add a surface interval of at least 1 hour. The UKDMC article suggests keeping at least 2 minutes of no-stop time on the computer, diving no more than three days in a row and making no more than two dives a day. Then, on the day:

• Skip the day if you feel unwell, anxious or seasick, or your glucose is not in its usual stable pattern (SPUMS).
• No alcohol for 24 hours before diving (ADS) and no missed meals (SPUMS). The 2020 review suggests eating 1.5-2 hours, preferably 3 hours, before the dive.
• Make only the insulin or tablet changes agreed with your diabetes team. For people on injections, the 2020 review calls a 20% cut in long-acting insulin possibly reasonable for moderately long, strenuous or repeated dives.
• Drink extra water. SPUMS suggests 1000-1500 ml over several hours before the first dive; UKDMC doctors say adequately hydrated, but not over-hydrated.
• Test at 60, 30 and 0 minutes and apply the limits your doctor agreed with you.
• Carry glucose gel in a reachable pocket, give your buddy some too, and leave glucagon and your meter at the surface with someone who can use them.
• Tell your buddy and the dive leader about your diabetes and the 'L' signal; UKDMC also wants the dive manager to know the dive profile.
• Test again at the end of every dive. The same pre-dive rules apply before the next one.
• Keep checking often for 12-15 hours after diving, because glucose can fall late (DAN).
• Log every dive with glucose results, carbohydrate and insulin doses, and use the log to plan the next one (DAN).
• Report any odd symptom to your buddy or the dive manager at once; do not put it down to diving (UKDMC).