Can You Scuba Dive With High Blood Pressure? Limits and Medication

Can you scuba dive with high blood pressure?

Most people with treated, well-controlled high blood pressure can. DAN states that controlled hypertension is not a contraindication for diving, although it is one of several cardiovascular risk factors. The physician guidance that goes with the international diver medical form says treated hypertension with adequate control is acceptable when no other risk factors call for screening for coronary artery disease.

It is common among divers. A 2020 review by the Dutch Society for Diving Medicine cites surveys in which 12% of Dutch divers and 24.6% of US divers reported hypertension.

The form you complete before a course decides if you need a doctor, as our diver medical questionnaire guide explains. Any prescription medicine makes question 10 a yes, which sends you to a physician. Box B, for people over 45, is the only place the 2026 form names high blood pressure, so someone aged 45 or under with untreated high readings may never be asked.

This is general information, not medical advice. A physician decides fitness to dive, ideally one trained in diving medicine. 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 blood pressure matters underwater

Immersion, cold and effort all load the heart at once. A cardiologist on a DAN Alert Diver expert panel explains that immersion moves up to 700 ml of blood from the legs into the chest. That raises the pressure in the right atrium by 16-18 mmHg, increases cardiac output by about 30% and nudges blood pressure up slightly. The Dutch review adds two more pushes: cold water narrows the blood vessels in the skin and limbs, which drives more blood to the core, and exercise can temporarily raise arterial pressure substantially. It warns that a blood pressure already well above normal before a dive may add up to a strain that could trigger a cardiovascular event.

According to DAN, high blood pressure and heart disease have for many years been the chronic conditions most often reported as contributing to diving deaths. In its 2004 report, more than 14% of the fatalities had a chronic history of high blood pressure, heart disease or both.

The long-term damage matters as much as the reading on the day. DAN lists coronary artery disease, heart failure, atrial fibrillation, chronic kidney disease, stroke and loss of vision as long-term effects of hypertension, and asks that a doctor monitor the heart and kidneys. The UHMS guidance treats left ventricular hypertrophy (a thickened heart muscle wall) as a relative risk, because it can cause arrhythmias set off by exercise or immersion.

Immersion pulmonary oedema and its link with hypertension

Immersion pulmonary oedema (IPE, also written IPO) is fluid leaking from the blood into the air sacs of the lungs while a person is in the water. A 2024 joint statement from SPUMS and UKDMC lists cough, shortness of breath, frothy or pink sputum, chest tightness and confusion among the signs, and says it can be fatal.

Immersion shifts blood to the chest and raises pressure in the lung capillaries, while breathing in the water happens at a negative airway pressure that regulator resistance and dense gas can make worse. These changes happen in nearly everyone, so extra factors are usually needed. The statement lists a previous episode, female sex, older age, and hypertension or heart disease, plus colder water, breathing resistance from equipment, severe exertion and excessive hydration.

Hypertension is the most frequent cardiovascular disease predisposing to IPE, according to a 2019 review by cardiologist Peter Wilmshurst. In a 1989 Lancet study of 11 people who had pulmonary oedema while diving or swimming, 7 became hypertensive over an average follow-up of 8 years. At Duke University, 72.2% of 36 people with IPE had at least one significant medical condition at the time, hypertension among them. The Dutch review cites a small study in which 8 of 10 divers with IPE were on blood pressure treatment, and notes that hypertension is linked with a higher chance of the oedema coming back.

Advice on diving again after an episode conflicts, and the newer statements are stricter. In the 2011 DAN panel, two of three physicians said many divers can return once symptoms resolve or a cardiac evaluation is normal, with further heart testing first for anyone with hypertension. The 2023 UHMS guidance calls a single episode a relative risk that may rule out diving if no modifiable risk factor is found, and repeated episodes a severe risk. The 2024 SPUMS and UKDMC statement strongly advises against any further compressed gas diving after one episode, says limiting depth is not an acceptable way to prevent it, and recommends lifelong regular blood pressure checks.

What the guidelines say: UK, US, Australia and Europe compared

They agree that controlled blood pressure is compatible with diving. UKDMC and EDTC also rule out diving when hypertension has caused end-organ damage, which UKDMC defines as kidney, eye or heart complications. They disagree on the number. UKDMC draws the line at 140/90 mmHg. SPUMS and the Dutch Society for Diving Medicine rule out diving only above 160/100 until it is treated. The UHMS guidance gives no figure and works from overall heart risk instead.

SPUMS 2025 repeats several of the Dutch recommendations almost word for word, including the advice that diving may affect which blood pressure drug is chosen. The European EDTC standard covers working divers, including instructors and other recreational dive professionals.

Blood pressure medication and diving

Most are compatible with diving. DAN says that with controlled blood pressure and no organ damage, the main concern is side effects, and most drugs are fine as long as those are minimal and performance in the water is not significantly reduced. The sources rank the drug classes differently. Other medicines common later in life are covered in our guide to learning to dive after 50.

Two effects are specific to diving. The Dutch review warns that calcium antagonists can cause a sudden drop in blood pressure as you leave the water, when the blood held in the chest during immersion moves back to the limbs, and suggests getting out gradually. For thiazide diuretics, it calls the loss of plasma volume modest, but on a tropical trip the drug can make fluid losses from heavy sweating, repeated dives and travellers' diarrhoea much worse. Dehydration is commonly thought to raise decompression sickness risk, though the review calls the evidence very limited.

Fluid cuts both ways. The UHMS guidance and the SPUMS/UKDMC statement list over-hydration as a risk factor for IPE, and one diver in Wilmshurst's case series had drunk more than 3 L in the hours before the dive on which he developed it. The Dutch advice is to hydrate properly before and after diving, not to drink as much as possible.

Can you dive on beta-blockers?

Sometimes, after testing. DAN explains that beta-blockers can reduce the heart's capacity for exercise, and if a drug restricts the heart during exercise, the risk of losing consciousness rises, which could be fatal underwater. Doctors therefore often recommend a stress test. Divers who reach a strenuous level of exercise without severe fatigue may be cleared, and should then avoid extreme exertion.

UKDMC puts a number on it: on an exercise stress test, the diver should reach a heart rate of at least 90% of (220 minus age) beats per minute. For a 55-year-old, 220 minus 55 is 165, and 90% of 165 is 148.5, so about 149 beats per minute. UKDMC also wants no sign of bronchospasm (narrowing of the airways), preferably checked with lung function tests on and off the drug, the same spirometry described in our article on diving with asthma.

The Dutch review explains the airway concern: in susceptible people, beta-blockers can lower FEV1 by blocking beta-2 receptors in the airways, an effect that seems to fade with long-term use. It also reports multiple IPE cases in divers on beta-blockers seen at the Sharm el Sheikh hyperbaric facility, though no controlled studies have tested this. The EDTC standard adds that beta-blockers can distort fitness tests that use heart rate, so tell the examiner what you take.

What a diving doctor checks

The readings come first, judged against the limits in the table above. After that, four things.

• Organ damage. UKDMC rules out diving if hypertension has damaged the kidneys, eyes or heart, including an enlarged heart, and EDTC also requires no end-organ damage. SPUMS recommends checking people with hypertension for signs of cardiac ischaemia or dysfunction, and a resting ECG for divers aged 45 or over.
• Exercise capacity. DAN asks physicians to make sure divers with hypertension can tolerate high exertion for at least 5-10 minutes, because conditions can change or an emergency can demand it. The UHMS fitness target of 6 METs is explained in our weight limit article.
• Overall heart risk. The UHMS guidance says anyone with a predicted 5-10 year cardiovascular risk above 10% should be investigated for coronary disease, unless they give a credible history of exercise capacity. SPUMS uses a 10-year risk for divers aged 45 and over: under 10% may proceed, higher risk calls for a coronary calcium score, and above 20% for a CT angiogram or a functional stress test.
• Side effects. DAN lists dehydration, dizziness, chronic cough and reduced exercise capacity as drug side effects that can rule out diving and need a physician's attention.

Before you book a course: a checklist

Start a few weeks before the trip.

• Get your blood pressure treated and stable first. DAN says divers with hypertension should be under a physician's care and able to tell the operator it is controlled and without complications.
• Answer the medical form honestly: question 10 for any prescription, box B if you are over 45, and box A if you have had immersion pulmonary oedema or take medication for a heart condition.
• See a physician trained in diving medicine, with your medication list, home readings and any ECG or echocardiogram results. DAN's Medical Information Line gives referrals.
• Ask if your drug suits diving, since SPUMS and the Dutch society both say diving may affect the choice. Do not switch or stop it on your own.
• After a new drug or dose change, allow several weeks to watch for side effects before diving (DAN).
• On a beta-blocker, expect an exercise test and possibly lung function tests (UKDMC).
• Learn the warning signs of IPE. SPUMS says divers with hypertension should know the symptoms and abort a dive at once if they appear.
• Plan conservative dives. The Dutch society recommends a wider safety margin against decompression sickness, and EDTC lists avoiding cold exposure, deep air dives and high-oxygen mixes as possible restrictions.

When to end a dive, and when to stop diving

End the dive if breathing gets harder than the effort explains. The SPUMS and UKDMC statement lists what a buddy may notice: coughing, faster breathing or gas use out of proportion to the work, a diver who believes the regulator has failed or the gas has run out, agitation and an urge to ascend.

Its first aid advice is to leave the water as soon as possible, ascend safely but skip the optional safety stop, float with positive buoyancy at the surface, give the highest oxygen concentration available, keep the diver sitting up, remove tight gear and transfer to hospital. If required decompression stops are missed, the diver also needs observation for decompression sickness and a call to the nearest recompression facility.

Stop diving and see a doctor before the next dive after any suspected IPE, and with chest pain, breathlessness, palpitations or fainting on exertion, which the UHMS guidance says should be investigated. DAN notes that headaches, particularly at the back of the head, are a common symptom of hypertension, and that nosebleeds and shortness of breath tend to appear only at life-threatening levels.