Hyperosmolar hyperglycaemic state (HHS) can happen when people with type 2 diabetes – or undiagnosed type 2 diabetes – have very high blood glucose levels, also called blood sugar levels. By the time HHS is diagnosed your blood sugar levels can often be over 40mmol/l.
You may not realise you have type 2 diabetes until you’re very unwell with HHS and diagnosed.
HHS can develop over many days. Through a combination of high blood sugar levels, dehydration and sometimes an illness, such as an infection. Or a cardiovascular event, such as a heart attack or stroke.
HHS is a life-threatening complication of diabetes that needs to be treated in hospital.
On this page we cover:
- What causes HHS?
- What is the difference between DKA and HHS?
- What are the symptoms of HHS?
- What is the treatment for HHS?
- How can I prevent HHS?
- Get support
What causes HHS?
HHS is caused by:
- extremely high blood sugar level
- extreme lack of water (dehydration).
HHS develops when blood sugar levels are too high, causing cells in your body to become dehydrated.
Normally, when your blood sugar levels are high and there isn’t enough insulin to move all the sugar into your cells, your kidneys remove extra sugar from your blood when you wee. This also means your body loses water.
If you don't drink enough water or keep eating and drinking sugary or carb-rich foods, you can become dehydrated. When this happens, the kidneys struggle to get rid of extra blood sugar causing a big increase in your blood sugar levels.
The loss of water makes the blood more concentrated. This is called hyperosmolarity. It means the blood has too much salt, glucose, and other substances. This draws water out of the body's organs, including the brain.
Doctors used to call it HONK - hyperglycaemic hyperosmolar non-ketotic coma. It was renamed HHS because it doesn’t always lead to a coma.
You may also develop HHS if you are ill, dehydrated or not able to take your normal diabetes medication. For example, if you have swallowing problems or feel sick.
Even if you’re taking your normal diabetes medication, your blood sugar often rises if you are ill. This is because of other hormones the body produces during illness.
What is the difference between diabetic ketoacidosis (DKA) and HHS?
People with type 2 diabetes can develop either diabetic ketoacidosis (DKA) or HHS, but DKA is more common in people with type 1 diabetes.
We don’t know why some people develop HHS instead of DKA.
In DKA there is a severe lack of insulin in the body. This means the body can’t use sugar for energy and starts to use fat instead. When this happens, chemicals called ketones are released. If left unchecked, ketones can build up and make your blood become acidic. This is why it is called acidosis.
In HHS there is enough insulin to stop acidosis and ketones but this means blood sugars can be much higher and dehydration very severe.
They are both very dangerous conditions and need immediate help. People usually feel more unwell quicker when in DKA so usually seek help sooner. Whereas some people who are developing HHS put symptoms down to other things and may take longer to seek help.
Both DKA and HHS are diagnosed in hospital with blood tests.
What are the symptoms of HHS?
Common symptoms of HHS include:
- weeing more often
- feeling very thirsty all the time
- feeling sick
- very dry skin
- feeling generally unwell
- confusion and, in later stages, feeling sleepy and a gradual loss of consciousness.
What is the treatment for HHS?
HHS is a potentially life-threatening emergency.
If you have HHS you need treatment as soon as possible.
You will need to go to hospital to have fluid and insulin through a drip.
This is to treat dehydration and bring blood glucose down to a safe level.
How can I prevent HHS?
- Look out for the symptoms of high blood sugar, sometimes called hypers, and see your GP if you are getting any of these symptoms (whether you have type 2 diabetes or not).
- Follow our tips for managing diabetes when you are unwell. Some people will know these as diabetes sick day rules.
- Keep taking your diabetes medications – even if you don't feel like eating. Unless you have been told to stop them during an illness such as when taking SGLT2 inhibitors sometimes called ‘gliflozins’.
- If you check your blood sugar at home you'll probably need to do it more often – at least every four hours, including during the night
- Contact your healthcare team if your blood glucose levels remain high – above 15mmol/l).
- Stay hydrated – have plenty of unsweetened drinks such as water or diluted sugar free squash.
- Keep eating or drinking – if you can’t keep food down try eating little and often. Try small snacks or drinks with carbohydrates in to give you energy. And contact your GP for advice.
Jordan had undiagnosed type 2 diabetes. Read his experience of HHS.
Get support
For more advice and support, talk to your healthcare team.
Or if you'd rather talk over the phone, our helpline is managed by our trained advisors who are ready to answer your questions or just listen.
Our reach out on our forum to other people with diabetes who can share their experiences.
