Brittle diabetes mellitus (or labile diabetes) is a term used to describe particularly hard to control type 1 diabetes.
Signs of brittle diabetes
Brittle diabetes presents as type 1 diabetes that is very difficult to control. People with brittle type 1 diabetes may experience the following symptoms: 
- Unpredictable, sharp changes in blood glucose levels without an obvious cause
- Frequent episodes of very high and very low blood sugar
- Greater likelihood and frequency of experiencing ketoacidosis and/or severe hypoglycemia
Likelihood of brittle diabetes
Brittle diabetes is relatively rare. Research suggests it is more common in females than males and tends to occur in young adulthood.
Brittle diabetes is less common in people over 40 years of age which suggests that brittle diabetes may, in some cases, resolve itself in time. 
How can brittle diabetes develop?
Brittle diabetes is often associated with stress, depression and other psychological issues. Stress can lead to acute and temporary insulin resistance. This means that the body does not respond to insulin and this can come on and disappear very quickly without warning. This can lead to distinct challenges when needing to judge insulin doses.
Additionally, other psychological issues may add further complications to the management of type 1 diabetes.
Not knowing when food will be digested can make it hard to judge when or how much insulin should be given.
Other problems that may result in brittle diabetes include:
- Insulin absorption problems
- Drug interactions
Managing brittle diabetes
As one of the main problems with brittle diabetes is unpredictable rises and drops in sugar levels, a reduced carbohydrate diet can help to reduce the wide swings in blood glucose, making sharp rises and drops less likely and less severe.
Diabetes technology such as insulin pumps, continuous glucose monitors or flash glucose monitors tend to give people more opportunity to control their blood sugar levels more effectively.
In the UK, you may be eligible to be put one or more of these technologies. This is more likely to be the case if brittle diabetes is putting you in danger or severely hampering your chance to lead a relatively normal life.
Addressing the causes of brittle diabetes
Identifying the factor or factors that may be causing brittle diabetes may help your health team to choose treatment strategies to address the causes. Your health team can help to identify which factors may be the cause of very difficult to control blood sugar levels.
If the cause is to do with autonomic neuropathy, your diabetes team may be able to offer you advice to help you safely manage insulin doses
If psychological issues are suspected, your health may be able to help you address these. Talking therapies and mindfulness-based therapies are examples of treatments that have had success in dealing with problems such as stress, anxiety and depression.