Frequently Asked Questions

Hyperbaric oxygen therapy (HBOT) is an evidence-based treatment that can help diabetic foot ulcers heal more quickly.

The treatment works by increasing the amount of oxygen in your blood, which supports tissue repair and fights infection. For many people with diabetes, HBOT can be a valuable part of their treatment plan, especially if other wound care treatments haven’t led to full healing.

However, HBOT can also affect blood glucose (sugar) levels, particularly in people who use insulin or an insulin pump. To help you prepare and stay safe during treatment, we’ve answered some common questions about how HBOT may affect your blood sugars, and how you can manage it.

1. Do glucose levels drop during HBOT – and why?

Yes - it’s common for blood sugar levels to become lower during HBOT, especially in people with diabetes. 

Research has shown that across people with diabetes (including those who need insulin, and those who don’t), blood glucose levels may decrease during HBOT by an average of around 36mg/dL.

Insulin-dependent patients may experience a higher drop in blood sugar levels, compared to those who are noninsulin-dependent. (1)

The exact reason for glucose levels falling is not fully understood. However, scientists have suggested that HBOT temporarily increases how sensitive your body is to insulin. It improves the way your cells absorb and use glucose, which means your blood sugar levels may fall more quickly than usual. (2)

Yes - studies have shown that people with type 1 diabetes are more likely to experience low blood sugar levels (hypoglycaemia or a “hypo”) during HBOT than those with type 2 diabetes. 

However, having type 1 diabetes doesn’t mean that HBOT isn’t an option for you.

Studies have found that low blood sugars during or immediately after HBOT occurs very infrequently, and severe or symptomatic hypoglycaemia is rare. (3)

There are often ways you can manage your blood sugar levels when you have HBOT, and it is reassuring to know that many patients with diabetes have benefited from HBOT with no adverse side effects. 

Many HBOT clinics recommend that your blood glucose level should be at least 120mg/dL before you enter the chamber for treatment. (1)

If your glucose level is below this threshold, you may be advised to eat or drink something to raise it before you start treatment. This is because each session lasts around 60 to 90 minutes, and your blood sugar is likely to fall during treatment. Starting with blood glucose levels above 120mg/dL may help to prevent a hypo during or after the session.

One study found that the higher the blood sugar before treatment, the lower the risk of a hypo. Having a glucose value of 140mg/dL before HBOT appeared to eliminate the risk of a hypo. (4) 

It is important to speak to your diabetes care team to establish a recommended blood sugar level for you before you start HBOT.

You should delay or reschedule your HBOT session if your blood glucose is too low – typically under 120mg/dL – at the time of your appointment. 

To ensure your safety and prevent symptoms of hypoglycaemia during treatment, it is important that you do not enter the chamber for treatment until your blood sugar levels are at the recommended level. At OxyGeneration, we will always try to accommodate delaying your treatment to a later session, or arrange to reschedule your appointment.

Talk to your diabetes healthcare provider if you’re unsure what a safe blood glucose level is for you, or to find out when it’s safe for you to proceed with HBOT.

If you have diabetes, it’s best to eat a balanced meal 1-2 hours before your HBOT session. Try to include protein, carbohydrates, and healthy fats to help keep your blood sugar steady. A nutritious meal will help to sustain your blood sugar level for longer, whereas trying to ‘top up’ your blood sugar level quickly with a sugary snack or drink can lead to blood sugar levels quickly falling again.

It is advisable to bring a fast-acting source of glucose into the chamber with you, such as a sugary drink like Lucozade Original, or 4-5 jelly babies. If your glucose levels drop during the session, these can be used to raise them quickly and safely.

 You may also choose to bring a slow-release supplement, such as a cereal bar or 2 digestive biscuits.

You should check your blood glucose:

• On arrival at the clinic before each HBOT session – depending on how you check your levels, you may also find it helpful to check your glucose at home to decide if a slow-release snack is required prior to attending

• After the session ends

Monitoring before and after treatment helps catch any significant falls in glucose level. 

If you have a compatible device, such as a continuous glucose monitor, you may also be able to monitor your glucose levels during treatment. If you’re using an insulin pump or continuous glucose monitor, make sure alerts are active and visible during treatment.

If you use an insulin pump, you might need to adjust your settings before treatment. Because HBOT can increase insulin sensitivity, your regular rate might cause your blood sugar to drop too far during the session.

Always speak to your diabetes care team before starting HBOT or making any changes to your insulin delivery. Some people can reduce their basal insulin rate or suspend their pump during treatment, but it depends on your individual needs.

For most people with type 1 and type 2 diabetes, HBOT is a safe treatment. Research shows that while blood sugar levels tend to drop during treatment, serious complications are rare.

In a study of 1,825 HBOT sessions completed by 77 people with diabetes, only 0.2% of treatments led to a glucose level below 70mg/dL. No patients experienced severe hypoglycaemia or needed emergency care. The study concluded that HBOT is safe for patients with well-controlled diabetes. (5)

Many people with diabetes have undergone HBOT for a variety of conditions, including to support the healing of diabetic foot ulcers, sports’ injuries, burns, radiation injuries, and more. With careful monitoring, preparation, and communication with your diabetes care team, HBOT can be a safe and effective treatment.

References

1https://www.hmpgloballearningnetwork.com/site/wmp/article/nutrition-411-managing-low-blood-glucose-levels-patients-undergoing-hyperbaric-oxygen

2 https://link.springer.com/article/10.1007/s00125-022-05797-0

3 Stevens SL, Narr AJ, Claus PL, Millman MP, Steinkraus LW, Shields RC, Buchta WG, Haddon R, Wang Z, Murad MH. The incidence of hypoglycemia during HBO2 therapy: A retrospective review. Undersea Hyperb Med. 2015 May-Jun;42(3):191-6.

4 By Trytko B, Bennett MH. Blood Sugar Changes in Diabetic Patients Undergoing Hyperbaric Oxygen Therapy. South Pacific Underwater Medicine Society Journal 2003:33(2); 62-69. Accessed via: https://www.woundeducationpartners.com/resources/rx-pad-blog/entry/question-how-should-i-manage-a-patient-that-has-a-low-pre-hyperbaric-treatment-blood-sugar.html

5 https://www.uhms.org/uhm-search/uhm-journal-volume-46/number-4/blood-glucose-levels-in-diabetic-patients-undergoing-hyperbaric-oxygen-therapy.html