Granulocyte-colony stimulating factor (G-CSF)

Having chemotherapy for cancer can affect your bone marrow, reducing your ability to make new white blood cells. This is called neutropenia and can increase your risk of infection. To help strengthen your immune system, your doctor may prescribe a treatment called G-CSF (granulocyte-colony stimulating factor). This helps your body to make more white blood cells.

G-CSF is given as an injection under the skin. This is usually done daily while you are having treatment. It can have some side effects, such as bone pain, itchy skin, or a fever. These are not usually severe, and lessen after G-CSF treatment stops.

G-CSF (granulocyte-colony stimulating factor)

What is G-CSF?

G-CSF is a special type of protein called a growth factor. It stimulates the bone marrow to make white blood cells. The bone marrow is a spongy material inside the bones where all of our blood cells are made.

Growth factors are made naturally in the body. They can also be made outside the body and used as treatments.

There are three different types of G-CSF that can be used:

  • lenograstim (Granocyte®)
  • filgrastim (Neupogen®, Nivestim®, Ratiograstim®, Zarzio®)
  • pegylated filgrastim (Neulasta®).

These treaments all work in similar ways.

Why G-CSF is given

G-CSF may be used during treatment with chemotherapy to shorten the length of time that your white blood cell numbers are low.

One of the main side effects of chemotherapy is a reduction in the number of white blood cells, which help to fight infection. A low white cell count is called neutropenia. If the number of your white blood cells is low you will be more prone to infections.

Usually the number of white blood cells is back to normal by the time the next dose of chemotherapy is due. But sometimes, if the levels of white blood cells are still low, the chemotherapy has to be postponed or the dose lowered.

G-CSF may be used to stimulate the production of white blood cells, thereby reducing the risk of infection, and helping to ensure chemotherapy treatments are given on time and at the planned dose. G-CSF isn't needed with all types of chemotherapy, as white blood cells usually recover on their own.

Stem cell collection

G-CSF may sometimes be used before high-dose chemotherapy to stimulate the bone marrow to make more stem cells. Stem cells are a special type of blood cell from which all other blood cells are made. The stem cells are collected from the blood and stored. They can then be given back to you after high-dose chemotherapy treatment and will make new blood cells to replace those you have lost.

What G-CSF looks like

G-CSF comes as a white powder to be dissolved in sterile water, or as a colourless fluid in a small glass bottle. It's also available in a pre-filled syringe.

How G-CSF is given

G-CSF is usually given as an injection under the skin (subcutaneously). You, or the person caring for you, can be taught how to inject G-CSF so that you can continue the treatment at home. Alternatively, the injections may be given by a district nurse or GP practice nurse.

The levels of white blood cells in your body will be tested regularly while you're having growth factor injections.

How often G-CSF is given

G-CSF is usually started a few days after chemotherapy and given daily. Your doctor or pharmacist will tell you how many injections you need. Pegylated filgrastim stays active in the body for longer, so it only needs to be given once after each cycle of chemotherapy.

Possible side effects of G-CSF

Possible side effects of G-CSF

When you're given G-CSF injections, the amount of G-CSF in your body becomes much higher than normal. This is why you may have side effects even though G-CSF is a naturally occurring substance. However, side effects aren't usually severe and lessen after G-CSF treatment ends. Each person’s reaction to treatment is different. Some people have very few side effects while others may experience more. The side effects described here won't affect everyone having G-CSF treatment.

We've outlined the most common side effects but haven't included those that are rare and therefore unlikely to affect you. If you notice any effects that aren't listed here, discuss them with your doctor or specialist nurse.

Bone pain

You may have some discomfort or a dull ache in the bones of your pelvis, back, arms or legs. Your doctor can prescribe painkillers if needed.

Red, itchy skin

Your skin may become red and itchy around the area in which the injection of G-CSF is given.

Fever and chills

Your doctor may prescribe painkillers, such as paracetamol, to help reduce your temperature and prevent chills.

Fluid retention

This may lead to swelling of the ankles or breathlessness.

It's important to let your doctor know straight away if you feel unwell or have any severe side effects, even if they're not mentioned above.

Additional information

Storing G-CSF

Filgrastim and pegylated filgrastim should be stored in the fridge. Lenograstim can be stored at room temperature. Follow any storage instructions given by your pharmacist.

Other medicines

Some medicines, including those that you can buy in a shop or chemist, can affect how G-CSF works. Tell your doctor about any medicines you are taking, including over-the-counter drugs, complementary therapies and herbal drugs.


There is a potential risk that G-CSF drugs may be present in breast milk, so women are advised not to breastfeed during this treatment and for a few months afterwards.

Non-cancer admission

If you’re admitted to hospital for a reason not related to the cancer, it’s important to tell the doctors and nurses looking after you that you are having treatment with G-CSF. You should tell them the name of your cancer specialist so that they can ask for advice.

Emergency contacts

It’s a good idea to know who you should contact if you have any problems or troublesome side effects when you’re at home. During office hours you can contact the clinic or ward where you had your treatment. Your specialist nurse or doctor will tell you who to contact during the evening or at weekends.

Back to Supportive therapies

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