Male patient with Anthony Nolan patient services staff member

Chronic lymphocytic leukaemia (CLL)

Chronic lymphocytic leukaemia is a type of blood cancer affecting white blood cell production and development over a long time. On this page, we explain CLL, its possible treatments and where you can look for support.

What’s on this page?

What is chronic lymphocytic leukaemia (CLL)?

Chronic lymphocytic leukaemia (CLL) is a type of blood cancer that affects your body over a long time – the main problem is that this leukaemia causes lymphocytes to develop too quickly. Lymphocytes are a type of white blood cell produced in the bone marrow that help your immune system work well.

Your lymphocytecells at their earliest stage are called ‘lymphoblasts’. We call these ‘immature’ cells. It means they haven’t yet developed fully and are in the early stages of growth.

If you have CLL, the lymphoblasts grow too quickly and don’t work properly. Over time, they gather in your lymphatic system and can cause large, swollen lymph nodes. They also fill up your bone marrow, stopping it from producing all the different types of healthy blood cells your body needs.

How many people are diagnosed with CLL?

In the UK, around 4,000 people are diagnosed with CLL every year. It's the most common type of leukaemia diagnosis for adults.

CLL is more common in men and people over 40, but the average age of diagnosis is around 70.

Treatments for CLL

CLL is a ‘chronic condition’, which means it develops very slowly. You might not need treatment for months or years. In comparison, acute conditions need treatment as soon as possible, such as acute lymphoblastic leukaemia (ALL).

In some cases, doctors might first try using chemotherapy or targeted cancer drugs to treat CLL. However, depending on the type of CLL, its response to treatment and your general health, you might get radiotherapy or a stem cell transplant.

If your body hasn’t responded well to initial treatment, or if your doctors think it’s unlikely to, they might offer an:

How many people have a stem cell transplant to treat CLL?

There were 16 stem cell transplants in the UK to treat CLL in 2023.

Where to find support for CLL

Anthony Nolan supports people with all sorts of conditions that might use stem cells or cell therapies for treatment. But other organisations support people affected by specific blood cancers like CLL.

To find out more about CLL symptoms, diagnosis and treatments, you can visit:

To find advice and support for living with cancer, you can visit:

Information last updated: 12/05/2025

Next review due: 12/05/2026