Dr Peter Wilmshurst has been a qualified doctor for over 25 years. He has served on the BSAC Medical Committee since 1977 and also advises the HSE on diving.
Are diabetics allowed to dive In Australia I was recently told that I could not dive because I am diabetic.

Regulations relating to diabetes and diving vary from country to country. Diving clubs in the UK (BSAC, SAA and SSAC) and in certain other parts of the world allow some diabetics to dive.
Some diabetics control their blood sugar levels with insulin injections, others take tablets and some use diet alone. Diabetes can produce unconsciousness if the blood sugar level is too high, but this is likely to happen only if the individual is unwell with another illness, such as an infection.
Unconsciousness can also occur when the blood sugar is too low, which might happen if the diabetic injects too much insulin or takes too little food. Unconsciousness in the water is likely to lead to drowning, so there are obvious concerns about allowing diabetics to dive if their blood sugar control is poor.
Diabetics are also more likely to have other problems that might cause incapacity in the water, including heart attacks and strokes, so in some countries all diabetics are banned from diving. In the UK we believe such bans are based on fear of litigation, which means that they are unfair and bad medical practice.
For a diabetic to be considered fit to dive in the UK, he or she must demonstrate good control of diabetes and the absence of any complications such as heart or kidney disease, which would indicate increased risk during diving.
Approval for a diabetic to dive is given by a medical referee, based on information from the individuals diabetic consultant and GP. The exact requirements are laid out in documents which can be obtained from the appropriate diving organisations.
Fat chances
I have just been for a diving medical and the doctor said my BMI is too high. How do you calculate BMI I am 1.72m (5ft 6in) tall and weigh 105kg (16.5 stone). Can you explain how this makes me unfit to dive

BMI stands for Body Mass Index and is a measure of obesity. It is calculated by dividing weight in kilograms by the square of height in metres. The above height and weight gives a BMI greater than 35. Normally a BMI of more than 30 disqualifies an individual from diving. The main reason is that obesity is often associated with lack of fitness.

Mother-to-be risks
What exactly are the recommendations for diving in pregnancy I am planning a trip to Malta and will be eight weeks pregnant on departure. Will I be restricted to snorkelling because of this

We dont have very good information about the risk of diving during pregnancy. This is because definitive data could be obtained only by deliberately doing research (called a prospective study) on a large number of pregnant women, and such research would be unethical.
Prospective animal research has given conflicting results and its hard to know whether any of the findings can be extrapolated to humans. We therefore have only anecdotal (observational) reports on women who dived during pregnancy, either because they were unaware that they were pregnant or because they decided to dive anyway.
This anecdotal evidence suggests that decompression illness and its treatment in a recompression chamber might be harmful to a foetus. Even shallow dives can result in pulmonary barotrauma and gas embolism which could require recompression treatment.
There is also some anecdotal evidence that deep dives (to greater than 30m) are associated with an increased risk of foetal abnormalities. There is a further suggestion that spontaneous abortion might be more common in women who dived during pregnancy, especially if they did more than one dive each day, or did dives requiring compulsory stops.
In summary, theres no definite proof that diving in pregnancy is unsafe, but if a woman wishes to be certain that the foetus will not be harmed, she should not dive during pregnancy. If she does, the UK Sport Diving Medical Committee recommends that she should aim to minimise her gas load.

Electronic pain relief
Can a person dive if they suffer from chronic pain for which they have a dorsal implant/spinal cord stimulator and take regular pethidine

The correct name for such a device is a dorsal column stimulator. This is an implanted device like a pacemaker, which stimulates the spine to modify the pain impulses entering from a particular region of the body.
The metal case of the stimulator would be compressed as hydrostatic pressure increases when a diver descends. If the diver goes deeper than the tolerance of the case, the electronic workings of the stimulator will be irreparably damaged.
A diver would have to know the details of pressure tests done on the dorsal column stimulator by the manufacturer, to ensure that he or she did not dive too deep. However, this is a little academic in this case. The use of narcotic analgesics such as pethidine by divers could lead to nitrogen narcosis at low partial pressures of nitrogen (in other words, at shallow depths) and this is too dangerous for diving to be permitted.

Seizures and breathlessness
My question involves two no-nos in diving: asthma and epilepsy. When I was a young child, I had frequent fits (also called seizures or convulsions). Between the ages of 3 and 15, I had none. When I was 15 I had scarlet fever with a high fever and had another fit. I am now 27, have had no fits since then and have not taken anticonvulsant (epilepsy) drugs since I was a child. Also as a teenager I had exercise-induced asthma but it was never very severe and I have not needed to use an inhaler or take any other asthma medication for six years. Can I become a recreational diver

The regulations relating to epilepsy and asthma vary from country to country and organisation to organisation. Some diving doctors take a strict view that anybody with a history of either epilepsy or asthma, no matter how mild or long ago, should never be permitted to dive. The UK Sport Diving Medical Committee takes a different view.
If an epileptic fit occurs under water it is likely to result in drowning but the risk of having another fit decreases considerably when one has been free from them for some years. We allow such individuals to dive (the Driver and Vehicle Licensing Authority permits resumption of car driving in the same way).
For divers, we also take into account the type of fits. Those associated with fever or occurring only during sleep seem to represent less risk. In some countries individuals are banned from diving for life if they have any history of convulsions but in the UK we would allow a person to dive as an amateur if they had had no fits for some years and were off anticonvulsant drugs. These drugs are believed to increase the narcotic effects of nitrogen under water, so individuals using them are not allowed to dive.
Asthma is a lung condition in which the smaller airways narrow when exposed to certain stimuli, such as allergens (animal furs and pollens), smoke and dust, emotional stress, cold, exertion and infection. When these airways narrow, it is more difficult for the individual to breathe out. This can cause breathlessness and also gas trapping, which might result in pulmonary barotrauma in a diver.
As far as asthma is concerned, some countries and diving organisations ban outright all asthmatics and even individuals who have grown out of the condition since childhood.
Most diving doctors in the UK take a more liberal view. We believe that individuals with well-controlled and mild asthma can be allowed to dive, and that they are less at risk of pulmonary barotrauma than smokers. However, these individuals must pass a medical assessment by a medical referee before diving is permitted.