G-CSF (Granulocyte-Colony Stimulating Factor)

G-CSF is a drug that’s most often prescribed after chemotherapy. It helps increase white blood cells called neutrophils that protect you from infection. Neutrophils are often destroyed during chemotherapy, causing a condition called neutropenia. G-CSF can also increase your number of stem cells before or after a stem cell transplant.


What is G-CSF (granulocyte colony-stimulating factor)?

G-CSF is a drug that helps your body to make more white blood cells called neutrophils. Neutrophils are the most common type of white blood cell you have. They help your body fight germs, like viruses and bacteria, that can cause illness, infections and disease.

G-CSF is short for “granulocyte colony-stimulating factor.” The name provides clues about what G-CSF does:

  • Granulocyte: A granulocyte is a type of white blood cell. There are three types of granulocytes: neutrophils, basophils and eosinophils. G-CSF stimulates your body to make neutrophils.
  • Colony-stimulating factor: A colony-stimulating factor is a protein that tells your cells what to do. G-CSF can tell an early form of a blood cell (stem cell) to become a neutrophil. It can tell a neutrophil to multiply so that you have more neutrophils.

G-CSF triggers cell changes within the spongy tissue inside your bones called bone marrow. Your bone marrow makes blood cells — including stem cells and neutrophils — and then releases them into your bloodstream.

What is G-CSF used for?

G-CSF is used to treat and prevent neutropenia, especially during cancer treatments. Neutropenia means having a lower-than-normal level of neutrophils. Having neutropenia can make it harder for your body to fight infections.

Your healthcare provider may prescribe G-CSF for various reasons.


G-CSF can spur your bone marrow to make more neutrophils so that you don’t get a serious infection or fever after chemotherapy. Chemotherapy drugs fight cancer by killing cancer cells. But chemotherapy can also kill healthy cells — including neutrophils. Neutropenia following chemotherapy is common and can even be life-threatening without treatment.

Stem cell transplant

You may need G-CSF before or after a stem cell transplant. You may need a transplant if you have cancer or blood disorders that cause abnormal blood cells.

Taking G-CSF before a stem cell transplant stimulates your bone marrow to release stem cells into your bloodstream. A healthcare provider collects the healthy stem cells. Then, the provider destroys the abnormal blood cells, often using chemotherapy drugs or radiation therapy. Finally, they inject the healthy stem cells back into your body so that they can develop into normal blood cells.

You may also need G-CSF if you’ve agreed to donate your stem cells to someone who needs them.

Other neutropenia-related conditions

You may need G-CSF if you have another condition that causes your neutrophils to be low. For example, some people are born with conditions that cause severe neutropenia. Others have neutropenia that doesn’t have a clear cause.

G-CSF can boost neutrophils in these cases, too.

What are the different types of G-CSF?

G-CSF is also known as filgrastim (Neupogen®). There are various forms of filgrastim, sold under different brand names. They’re called biosimilars. They’re not exactly the same as filgrastim, but they’re as safe and effective. They include:

  • Filgrastim-aafi (Nivestym®).
  • Filgrastim-sndz (Zarxio®).
  • Filgrastim-ayow (Releuko®).

Lenograstim (Granocyte™, Neutrogin™, Myelostim™) is another G-CSF with uses similar to filgrastim.

Pegfilgrastim (Neulasta®) is a long-acting form of filgrastim that stays in your body longer. This means that you don’t need as many injections of pegfilgrastim as you do with filgrastim.

Biosimilars include:

  • Pegfilgrastim-jmdb (Fulphila®).
  • Pegfilgrastim-cbqv (Udenyca®).
  • Pegfilgrastim-bmez (Ziextenzo®).
  • Pegfilgrastim-apgf (Nyvepria®).
  • Pegfilgrastim-pbbk (Fylnetra®).

Who needs to have G-CSF?

Not everyone who receives chemotherapy or who has neutropenia should have G-CSF. As with any drug, G-CSF has benefits and potential side effects. Sometimes treatment risks outweigh the benefits.

Your healthcare provider will consider various factors before prescribing G-CSF, including:

  • Your age.
  • Your health.
  • The type of cancer you have.
  • If this is your first round of chemotherapy.
  • How you responded to previous rounds of chemotherapy.
  • Whether you already have neutropenia or neutropenia symptoms (like a fever).

Your healthcare provider can explain why you are (or aren’t) a good candidate for G-CSF.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Procedure Details

What happens before taking G-CSF?

Your healthcare provider will need to know your complete medical history to ensure the medicine is safe. They’ll need to know about:

  • Any past or present conditions.
  • Any medicines you’re taking, including supplements.
  • Whether you’re pregnant or planning to become pregnant (you shouldn’t take G-CSF if you’re pregnant, trying to become pregnant or if you could impregnate someone).
  • Whether you’re breastfeeding (you shouldn’t take G-CSF if you’re breastfeeding).

Your healthcare provider will also need to know about any upcoming doctor or dentist visits you have. Every provider you see should know that you’re taking G-CSF. Your healthcare provider who’s prescribing G-CSF can explain steps you should take to ensure your other providers are informed about your medicine.

How is G-CSF administered?

Usually, you’ll get G-CSF as a shot that goes underneath your skin (subcutaneous injection). Or, you may get it as a drip into a vein (IV infusion). You’ll be in a hospital (or a similar type of medical setting that provides infusions) if you get it as an IV. The injection should take about 30 minutes.

You may need to go to a clinic for shots underneath your skin. Or, you may be able to give the shots to yourself at home. If this is the case, a healthcare provider will walk you through the steps to ensure you’re comfortable giving yourself the shot.


When is G-CSF administered?

G-CSF usually starts a day after chemotherapy ends or four to six days before stem cells are collected for a transplant. You’ll likely receive daily treatments unless you take the long-lasting form, pegfilgrastim. You may only need one shot between chemotherapy treatments if you take pegfilgrastim.

Your healthcare provider will tell you how many days you’ll need to receive G-CSF.

How long does it take G-CSF to work?

It takes several days (about a week) for your bone marrow to make new cells with G-CSF. Most people taking G-CSF after chemotherapy continue taking it until their levels return to normal.


What happens after I receive G-CSF?

Your healthcare provider will watch you closely for signs of neutropenia, like an infection or fever. They’ll also watch for treatment complications or side effects.

You may need regular bloodwork to check your neutrophil levels.

Risks / Benefits

What are the advantages of G-CSF?

G-CSF can prevent the most serious complications of neutropenia, which can be life-threatening without treatment. Studies about the effectiveness of G-CSF have shown that it can reduce your risk of infection. It can lower the risk of dying as a result of an infection.

G-CSF can also help chemotherapy treatments go more smoothly. It prevents your healthcare provider from delaying treatment or reducing your chemotherapy dose because your neutrophil count is too low.

What are the side effects of G-CSF?

Some side effects of G-CSF are common, while other, more serious side effects are rare. Most side effects go away once you stop taking G-CSF.

Side effects may include:

There are many other potential side effects.

Ask your healthcare provider what side effects you should expect based on the specific G-CSF drug you’re taking. Make sure you understand when you should contact your provider to report a side effect you’re experiencing.

What are the risks or complications of G-CSF?

If your healthcare provider recommends G-CSF, the benefits will likely outweigh the risks. Still, your provider will monitor your response to G-CSF and adjust your prescription as needed.

Rare (but serious) complications include:

Some studies have shown that some forms of G-CSF may increase your risk of certain types of cancer. Ask your healthcare provider to discuss potential risks with you before starting G-CSF.

Why does G-CSF cause bone pain?

Bone pain is a common side effect of G-CSF. Scientists don’t know for sure what causes the pain, but the discomfort may be like growing pains. When your bone marrow makes more blood cells faster than is typical, you experience the sudden expansion as bone pain.

Most people describe the pain as mild to moderate. Ask your healthcare provider if it’s safe to take over-the-counter pain relievers, like NSAIDs, to lessen the discomfort.

When to Call the Doctor

When should I see my healthcare provider?

Let your healthcare provider know about the side effects you’re experiencing while taking G-CSF. Before starting the medicine, talk with your provider about which treatment side effects require emergency medical attention.

Warning signs include:

Additional Common Questions

Is G-CSF the same as filgrastim?

Yes. Filgrastim is the most well-known form of G-CSF in the U.S.

A note from Cleveland Clinic

G-CSF can provide your body the boost it needs to fight germs if chemotherapy treatments have left you vulnerable to infections. Before starting treatment, discuss the benefits and risks of using G-CSF with your healthcare provider. Make sure you understand how to manage common side effects, and how and when to report symptoms.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 09/08/2022.

Learn more about our editorial process.

Cancer Answer Line 866.223.8100