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 (granulocyte-colony stimulating factor) is a targeted therapy drug that can be used with chemotherapy, or before and after a stem cell transplant.

Different types of G-CSF can be used. These include lenograstim (Granocyte®), filgrastim (Accofil®, Neupogen®, Nivestim®, Ratiograstim®, Zarzio®, TevaGrastim®) and pegylated filgrastim (Neulasta®).

It’s best to read this information with our general information about the type of cancer you have or the treatment you are having.

How G-CSF works

G-CSF is a type of protein called a growth factor. Growth factors are made naturally in the body, but can also be man-made. Some growth factors, such as G-CSF, make the bone marrow produce blood cells. Bone marrow is a spongy material inside bones.

G-CSF works in two ways:

  • It is given after chemotherapy to stimulate the bone marrow to make white blood cells. These blood cells help to fight infection.
  • It is given before a stem cell transplant to encourage more stem cells to be produced and released into the blood. These can then be collected for use in a transplant. Stem cells are blood cells at their earliest stage.

When G-CSF is used

With chemotherapy

You may have a low number of white blood cells during your chemotherapy treatment. The main white blood cells which fight infection are called neutrophils. When they are low you are neutropenic. If you have a low number of white blood cells, you are more likely to get an infection.

G-CSF may be used during treatment with chemotherapy so that you are neutropenic for a shorter time. G-CSF isn’t needed with all types of chemotherapy.

The number of white blood cells usually goes back to a normal level between cycles of chemotherapy. But if white blood cell levels are too low, chemotherapy may have to be delayed or given in a lower dose. G-CSF encourages the bone marrow to make white blood cells. This helps to reduce the risk of infection and allow chemotherapy treatments to be given on time and at the planned dose.

Collection for a stem cell transplant

Stem cells are blood cells at their earliest stage. Usually stem cells stay in the bone marrow while they develop into blood cells. G-CSF stimulates the bone marrow to make more stem cells. These then move (mobilise) from the bone marrow into the bloodstream, where they can be collected to be used in a transplant.

G-CSF may also be used after a stem cell transplant to help speed up the recovery of the new stem cells in the bone marrow.

  • Collecting your stem cells
    G-CSF can be used before you have high-dose chemotherapy. Stem cells are collected from your 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. This is sometimes called high-dose chemotherapy with stem cell support.
  • Collecting stem cells for donation
    If you are donating stem cells to another person you will have daily injections of G-CSF for several days. This will stimulate your bone marrow to make stem cells and increase the number of stem cells in the blood.

How G-CSF is given

G-CSF comes in a pre-filled syringe. It’s also available as a white powder or a colourless fluid that should be dissolved in sterile water.

G-CSF is usually given as an injection under the skin (subcutaneously). A nurse can show you, or a relative or friend, how to inject G-CSF so you can have it at home. The nurse will also give you advice about how to dispose of the needles safely. Sometimes a district nurse or practice nurse can give you the injections.

Some people may have G-CSF as a drip into a vein, which takes about 30 minutes. You will have this at the hospital or clinic.

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

With chemotherapy

If you are prescribed G-CSF, it’s usually started 24 hours or more after chemotherapy finishes and is given daily. Your doctor or pharmacist will tell you how many injections you need.

You may have a type of G-CSF called pegylated filgrastim, which stays in the body for longer. You will only need it once after each cycle of chemotherapy.

Stem cell collection

G-CSF is started 4-6 days before the planned date for the stem cell collection.

Possible side effects of G-CSF

When you have G-CSF injections, the amount of G-CSF in your body becomes much higher than normal. This can cause some side effects. These aren’t usually severe and get better when the G-CSF treatment stops.

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

We explain the most common side effects but haven’t included all of the rarer side effects that are unlikely to affect you. If you notice any effects that aren’t listed here, discuss them with your doctor or specialist nurse.

Serious and life-threatening side effects

Sometimes cancer drugs can result in very severe allergic reactions. These may be lifethreatening, but this is rare. Your cancer doctor and nurse can explain the risk of these side effects to you.

Contact the hospital

Your nurse will give you telephone numbers for the hospital. You can call them if you feel unwell or need advice any time of day or night. Save these numbers in your phone or keep them somewhere safe.

More information about this drug

We’re not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic medicines compendium (eMC).

Bone pain

This is very common. You may have some discomfort or a dull ache in the bones of your pelvis, back, arms or legs. This is because your bone marrow is making blood cells. Your doctor can prescribe painkillers, such as paracetamol.

Red, itchy skin

Your skin may become red and itchy around the area where you had the G-CSF injection. Having the injection in a different place on your body each time may help.


G-CSF may cause headaches. If this happens, tell your doctor or nurse. They can give you painkillers.

Bruising or bleeding

You may bruise or bleed more easily. This is because G-CSF can affect the blood clotting cells, called platelets, in your blood. This improves after treatment stops. Talk to your doctor or nurse if you are worried about this.

Fever and chills

Your doctor may prescribe paracetamol if you have a temperature and chills.

Sickness or reduced appetite

You may feel sick or not feel like eating while having G-CSF treatment. If this happens, talk to your doctor or nurse. They can give you anti-sickness drugs to help. These feelings should improve when treatment stops.

Bowel changes

You may be constipated or have diarrhoea while you are having G-CSF treatment. This should get better when treatment stops. Talk to your doctor or nurse if this is a problem for you. Try to drink at least two litres (three and a half pints) of fluids every day.

Left side or tummy discomfort

G-CSF can cause your spleen to get slightly bigger which might be uncomfortable on your left side, your tummy or your left shoulder. Tell your doctor straight away if you notice any discomfort or pain in these areas. Your spleen should go back to its normal size once treatment stops.

Liver changes

G-CSF may affect how your liver works. This is usually mild and goes back to normal after treatment. You will have blood tests to check how well your liver is working.

Build-up of fluid

This may lead to swelling of the ankles or breathlessness. This is quite rare. Talk to your doctor or nurse if you notice this.

Allergic reaction

Very rarely, people have an allergic reaction to G-CSF. The signs include a rash, swallowing or breathing problems, or swelling of your lips, face, throat or tongue. Contact the hospital straight away if you have any of these signs. Do not have any more G-CSF injections until you have spoken to your doctor.

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 here.

Other information about G-CSF

Storing G-CSF

Follow any storage intructions given by your pharmacist. Some G-CSF injections should be stored in the fridge. Take the injection out of the fridge 30 minutes before you use it.

Other medicines

Some medicines, including ones 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.

Treatment with G-CSF shouldn't be started until at least 24 hours after chemotherapy finishes.


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

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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