Haematology
G-CSF (growth factors)
Filgrastim, pegfilgrastim, lenograstim — Injections that prompt the bone marrow to make more infection-fighting white cells (neutrophils).
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
Quick answer
What is G-CSF (growth factors)?
G-CSF medicines are injections that stimulate the bone marrow to make more neutrophils — the white blood cells that fight infection. They are used mainly to prevent or shorten the dangerous dip in neutrophils after chemotherapy, and to collect stem cells for transplant.
- How it works: Granulocyte colony-stimulating factor is a natural signal that tells the bone marrow to produce neutrophils and release them into the blood.
- In practice: In practice granulocyte colony-stimulating factors (G-CSF — filgrastim, the longer-acting pegfilgrastim, and lenograstim) are injections that drive the bone marrow to produce and release more neutrophils, the white cells that fight bacterial infection.
What it is
G-CSF medicines are injections that stimulate the bone marrow to make more neutrophils — the white blood cells that fight infection. They are used mainly to prevent or shorten the dangerous dip in neutrophils after chemotherapy, and to collect stem cells for transplant.
How it works
Granulocyte colony-stimulating factor is a natural signal that tells the bone marrow to produce neutrophils and release them into the blood. These medicines are manufactured versions of that signal, so after chemotherapy the neutrophil count recovers faster, lowering the window of infection risk. The same drive on the marrow is what causes the characteristic bone pain.
In practice
In practice granulocyte colony-stimulating factors (G-CSF — filgrastim, the longer-acting pegfilgrastim, and lenograstim) are injections that drive the bone marrow to produce and release more neutrophils, the white cells that fight bacterial infection. Their main uses are to shorten the period of dangerously low neutrophils after chemotherapy (reducing the risk of neutropenic sepsis), to allow chemotherapy to be given on schedule, to treat some congenital or acquired causes of low neutrophils, and to mobilise stem cells into the blood so they can be collected for a stem-cell transplant. Pegfilgrastim is given once per chemotherapy cycle; filgrastim/lenograstim are given as daily injections over several days. The practical themes are: bone pain is very common (a sign the marrow is working hard) and is usually manageable with simple measures; the spleen can enlarge and, rarely, rupture, so left-upper-abdominal or shoulder-tip pain is reported; rare lung and allergic reactions can occur; and blood counts are monitored to time and stop treatment. They are supportive treatment — they do not treat the underlying cancer — and are used according to the regimen's risk of febrile neutropenia.
Examples
Practical use
How to take it & use it well
- It is given as an injection under the skin to prompt your bone marrow to make more neutrophils, the white cells that fight bacterial infection.
- Depending on which type you have, it is given either as a single injection once per chemotherapy cycle, or as daily injections over several days.
- If you give it yourself at home, you will be shown how to inject under the skin and to rotate the site each time to spare the skin.
- Expect aching bones a day or two after the injection, as this is very common and is a sign the marrow is working hard; it usually eases with simple pain relief.
- Report pain in the left upper side of your tummy or at the tip of your left shoulder promptly, as very rarely the spleen can enlarge or rupture.
- Keep to your blood-test and injection schedule, and still report any fever urgently, as this supports your immune system but does not remove the need for infection precautions.
Common uses
- Preventing/shortening neutropenia after chemotherapy
- Reducing neutropenic sepsis risk and keeping chemo on schedule
- Mobilising stem cells for collection before transplant
Monitoring
- Full blood count (neutrophils) to guide timing and duration
- Bone pain and tolerability
- Spleen size/abdominal pain and signs of allergic or lung reactions
Weighing it up
Advantages & disadvantages
Advantages
- It shortens the dangerous period of very low neutrophils after chemotherapy, reducing the risk of serious infection and neutropenic sepsis.
- It can help your chemotherapy be given on schedule rather than being delayed because of low blood counts.
- It can treat some people with congenital or acquired causes of persistently low neutrophils.
- It can mobilise stem cells into the blood so they can be collected for a stem-cell transplant.
- The longer-acting form, pegfilgrastim, needs only one injection per chemotherapy cycle, which is convenient.
Disadvantages
- Bone and muscle aches are very common, and although usually manageable they can be uncomfortable.
- Rarely the spleen can enlarge and even rupture, which is why certain pains must be reported promptly.
- Rare lung problems and allergic reactions can occur, so any breathlessness or rash is taken seriously.
- It is supportive treatment that helps your white cells, but it does nothing to treat the underlying cancer itself.
- It involves injections and regular blood tests rather than being a simple tablet.
Key safety principles
What to watch for
- Bone and muscle aches are very common (the marrow working hard) and usually settle with simple measures.
- The spleen can enlarge and, rarely, rupture — report pain in the left upper abdomen or the tip of the left shoulder.
- Rare lung problems and allergic reactions can occur; blood counts are monitored to time and stop treatment.
Key interactions
What to avoid or check alongside
- It is supportive treatment used around chemotherapy, and the timing is planned carefully so it is not given too close to the chemotherapy itself.
- Your blood counts are monitored closely, as this is how your team time the injections and decide when to stop treatment.
- Report fever or signs of infection urgently regardless of this medicine, as it supports but does not replace your infection precautions and antibiotics if needed.
- Left upper tummy or left shoulder-tip pain should be reported promptly, as it can signal a rare problem with the spleen that needs checking.
- Tell your team about all your other medicines and any new symptoms, especially breathlessness or rash, so rare lung or allergic reactions can be acted on quickly.
Patient & carer advice
- Aching bones a day or two after the injection are expected and usually ease with simple pain relief
- Report pain in the left side of your tummy or your left shoulder tip promptly
- Keep to your blood-test and injection schedule, and still report fever urgently — this supports your immune system but does not replace infection precautions
Use with
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Answers
G-CSF (growth factors): frequently asked questions
What is G-CSF and what is it for?
G-CSF stands for granulocyte colony-stimulating factor. It is an injection that drives your bone marrow to make more neutrophils, the white cells that fight bacterial infection. Its main uses are to shorten the period of dangerously low neutrophils after chemotherapy, to keep chemotherapy on schedule, to treat some causes of low neutrophils, and to collect stem cells for transplant.
Why do my bones ache after the injection?
Aching bones, often a day or two after the injection, are very common and are simply a sign that your bone marrow is working hard to produce white cells. It is expected rather than a sign of harm and usually settles with simple pain relief. Tell your team if it is severe or not easing, as they can advise.
What is the pain in my left side I have been warned about?
Very rarely, G-CSF can cause the spleen, which sits in the upper left of your tummy, to enlarge or even rupture. Pain in the left upper part of your tummy or at the tip of your left shoulder can be a warning sign of this. It is uncommon, but report such pain promptly so it can be checked.
Does this mean I am protected from infection?
It supports your immune system by boosting your infection-fighting white cells, but it does not make you immune. You still need to take your usual infection precautions, and crucially you must still report any fever urgently, as infection during low counts can be serious. Keep to your blood tests and injection schedule alongside these precautions.
Does G-CSF treat my cancer?
No. G-CSF is supportive treatment that protects your white-cell counts so that chemotherapy can be given safely and on time. It does not treat the cancer itself; that is the job of your chemotherapy or other anti-cancer treatment. Think of it as a helper that keeps you safer during treatment rather than a treatment for the disease.
Authoritative sources
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