Sickle Cell Disease (SCD) is an inherited blood condition that can cause episodes of severe pain, tiredness and other health complications. Sickle Cell Disease (SCD) affects haemoglobin, the protein in red blood cells that carries oxygen around the body. It can cause periods of severe pain, anaemia, fatigue and other health complications, although experiences vary considerably from person to person.
It is a lifelong condition, but with access to appropriate healthcare, treatment and support, many people with SCD live active and fulfilling lives. People with Sickle Cell Disease may feel well at some times and need more support at others. Pain episodes can happen unexpectedly, and symptoms such as fatigue are not always visible to the people around them.
Everyone experiences SCD differently. Greater understanding, flexible environments and access to appropriate healthcare can help remove many of the barriers people face in everyday life.
Sickle Cell Disease can be non-visible
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7.74 million people were living with Sickle Cell Disease globally in 2021 (World Health Organization) -
515,000 babies were born with Sickle Cell Disease worldwide in 2021 (World Health Organization) -
Pain episodes can happen suddenly and can vary in frequency and severity (World Health Organization) -
SCD can cause anaemia and fatigue because affected red blood cells have a shorter lifespan (World Health Organization)
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SCD can affect many parts of the body with complications including stroke, infections and kidney problems (World Health Organization)
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SCD is inherited and cannot be caught or passed between people through contact (World Health Organization)
What is Sickle Cell Disease?
Sickle Cell Disease is a group of inherited blood conditions.
Red blood cells normally carry oxygen around the body. In someone with SCD, some red blood cells can become harder, less flexible and curved in shape.
These cells can sometimes have difficulty moving through small blood vessels. This may reduce blood flow and cause episodes of severe pain, often called a sickle cell crisis or pain crisis.
SCD can also cause anaemia because affected red blood cells do not last as long as usual. This can contribute to tiredness, weakness or breathlessness.
Experiences vary considerably. Some people experience frequent pain or other complications, while others may have long periods when they need little additional support.
Many barriers associated with SCD also come from a lack of understanding, inflexible environments, unequal access to healthcare and people's experiences of pain or fatigue not being recognised by others.
What causes Sickle Cell Disease?
Sickle Cell Disease is inherited through genes passed on by biological parents.
It affects haemoglobin, which is the part of a red blood cell that carries oxygen around the body.
A person develops Sickle Cell Disease when they inherit particular haemoglobin gene variants from both biological parents.
Someone who inherits one sickle cell gene (haemoglobin S) and one normal haemoglobin A gene has sickle cell trait, rather than Sickle Cell Disease.
Sickle Cell Disease:
- Is inherited
- Is present from birth
- Is not contagious
- Cannot be caused by someone's lifestyle or choices
SCD occurs around the world. It is particularly common among people with ancestry from regions where malaria has historically been common, including parts of Africa, the Mediterranean, the Middle East, India and South Asia.
Types of Sickle Cell Disease
Sickle Cell Disease is the name for a group of related inherited blood conditions.
Some of the main types include:
- HbSS (Sickle Cell Anaemia): where a person inherits two haemoglobin S genes.
- HbSC disease: where a person inherits one haemoglobin S gene and one haemoglobin C gene.
- HbS beta thalassaemia: where a person inherits a haemoglobin S gene alongside a beta thalassaemia gene variant.
There are also other, less common forms of SCD.
Knowing the type of SCD does not tell you exactly how someone will experience the condition. People with the same type may have very different experiences and support requirements.
Common symptoms and signs
Sickle Cell Disease can affect people in different ways, and experiences can change over time.
Pain
- Episodes of severe pain that may happen unexpectedly
- Pain affecting different parts of the body
- Recurring or persistent pain
- Periods when pain may make everyday activities more difficult
Fatigue and reduced energy
- Tiredness or reduced energy
- Weakness
- Breathlessness
- Dizziness or light-headedness
Other experiences
- Increased susceptibility to some infections
- Yellowing of the eyes or skin, known as jaundice
- Changes in growth during childhood
- Joint damage causing varying degree of disability
SCD can also be associated with complications such as acute chest syndrome, stroke and problems affecting organs including the kidneys. Not everyone will experience all of these, and someone's experiences and support requirements can change over time.
Look out for these Sunflower icons
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I have a non-visible disability -
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I may need a place to sit down and rest
Important note
This information is intended for awareness and education only. It is not a diagnostic tool and should not be used to identify or diagnose Sickle Cell Disease or any other condition.
If you have concerns, please seek advice from a qualified healthcare professional.
Sources
World Health Organization (WHO) Sickle-cell disease
https://www.who.int/news-room/fact-sheets/detail/sickle-cell-disease
World Health Organization Management of Sickle Cell Disease in children and adolescents
https://www.who.int/publications/i/item/9789240122666
World Health Organization Management of Sickle Cell Disease during pregnancy, childbirth and the interpregnancy period
https://www.who.int/publications/i/item/9789240109124
Sickle Cell Disease Coalition
https://www.scdcoalition.org/
The content on this page has been reviewed by Sickleverse and the Sickle Cell Society, August 2026.
About The Sickle Cell Society
The Sickle Cell Society is the UK’s only national charity supporting and representing people affected by sickle cell disorders. Established in 1979, it works with people living with sickle cell, families and healthcare professionals to raise awareness, improve care and empower individuals to achieve their full potential.
The Society advocates for equal access to high-quality, sensitive and confidential support and services for everyone affected by sickle cell.
About Sickleverse
Sickleverse is a digital education and community platform helping people affected by sickle cell disease better understand their health, navigate care and feel more confident managing the condition.
Founded by Dr Lewis Thomas, a former GP who also lives with sickle cell disease, Sickleverse combines accessible health education with lived experience to make complex information easier to understand. Its wider mission is to improve health literacy, self-advocacy and awareness of sickle cell, while helping employers, organisations and the wider public better understand the realities of living with the condition.
For further information, please visit www.sickleverse.com or contact Lewis@sickleverse.com.