Hematologist
CION Cancer Clinics
G-CSF injections before donation: what they feel like and what helps | CION Cancer Clinics
Most donors feel bone ache, headache and tiredness during G-CSF injections, rather like the start of a flu. The injections are given once a day for four or five days, and the ache usually eases within a few days of stopping. Pain under the upper left ribs or at the left shoulder tip needs a same-day call. This page covers what is common, what helps and what to avoid. At CION Cancer Clinics, our haematology team assesses whether a transplant or CAR-T fits your situation and coordinates care with qualified centres.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- How will the G-CSF injections make you feel?
- Which side effects do most donors notice?
- What do the injection days look like?
- What can you do to feel better, and what should you avoid?
- What do the terms on your schedule mean?
- What worries do donors have about the injections?
- Common questions about G-CSF injections
The short answer
How will the G-CSF injections make you feel?
Most donors feel achy. The injections cause bone pain, usually in the lower back, hips and thighs, along with headache and tiredness. It feels a lot like the start of a flu, and it fades within a few days of the last injection.
Why the ache happens
G-CSF is a growth factor, a copy of a signal your body already makes. It tells the marrow inside your bones to make more white cells and stem cells, and to push them out into the blood. That busy marrow sits inside the large bones, which is why they ache. The ache is a sign the injection is doing its job, not a sign of damage.
What this page cannot tell you
Everyone reacts differently. Some donors barely notice the injections. Others need to take time off work. How you feel does not predict how many cells will be collected. Your own donor doctor, who knows your health check results, is the person to ask about your situation.
Your dose is worked out by the donor team from your weight. Never adjust it or skip an injection yourself.
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Call the donor team the same day
Pain under the ribs on the upper left side of the belly, or pain at the tip of the left shoulder, needs checking the same day. It can mean the spleen has swollen. This is uncommon, but it matters. Also call at once for breathlessness, a rash with swelling of the face, or bleeding you cannot explain. If you cannot reach the team, go to the nearest emergency department or call 108, and say you are a stem cell donor having G-CSF injections.
Not sure whether this applies to you?
Ask an oncologistWhat is common
Which side effects do most donors notice?
These are expected. They are uncomfortable, and they settle after the injections stop.
Bone and back ache
The most common effect by far. It is usually worst in the lower back, hips, breastbone and thighs, and often builds over the injection days.
What donors say helps
- A warm bath or hot water bottle
- Gentle walking rather than bed rest
- Pain relief the team has approved
Headache
Often dull and steady. Drinking plenty of water helps many people. A severe or unusual headache should be reported to the team.
Tiredness and flu-like feelings
Feeling run down, slightly feverish or achy all over. You may want to sleep more than usual. Plan lighter days if you can.
Smaller things
Some donors notice a poor appetite, feeling sick, trouble sleeping or redness where the needle went in.
A raised white cell count on a blood test during these days is expected, and is the point of the injections.Day by day
What do the injection days look like?
The first injection
A nurse gives it under the skin of your belly or upper arm, and shows you what to expect. Some centres teach donors or a family member to give later injections at home.
The middle days
You have one injection each day, for four or five days in total. The ache often builds from the second or third day. Carry on with light daily activity, and keep drinking water.
Blood tests
The team may check your blood count and the number of stem cells in your blood. This tells them when to start collecting.
Collection day
You may have a last injection that morning. The collection starts, and the ache begins to ease once the injections stop.
Getting through it
What can you do to feel better, and what should you avoid?
Ask the donor team, at the health check, which painkiller you may take. Many teams are happy with paracetamol. Some prefer you to avoid medicines that affect bleeding, such as aspirin and ibuprofen, because your platelet count can dip after collection. Get the answer in writing before the first injection.
Look after the basics
Drink plenty of water, eat regular meals and sleep when you can. Avoid alcohol during these days. Gentle movement often eases stiffness better than lying still.
Avoid knocks to your belly
Because the spleen can swell a little, skip contact sports, heavy lifting and rough play with children until the team says it is fine. This is a sensible precaution rather than a sign that anything is wrong.
Plan your week
If your job is physical, ask your employer for lighter duties or leave. Arrange travel to the centre so you are not riding a two-wheeler through traffic while achy and tired, especially on collection day.
Tell your family what to expect
Parents and spouses often worry when a healthy donor suddenly looks unwell. Explain beforehand that the ache is expected and temporary. It helps to have one person at home who knows the donor team's number and the warning signs described above.
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On your papers
What do the terms on your schedule mean?
- G-CSF
- Granulocyte colony-stimulating factor. A growth factor that makes the marrow release stem cells into the blood.
- Filgrastim
- The generic name of the G-CSF medicine most often used for donors. Several brands exist.
- Mobilisation
- Moving stem cells out of the bone and into the bloodstream, so they can be collected from a vein.
- CD34 count
- A blood test that counts stem cells in the blood. It helps decide when collection starts.
- Spleen
- An organ under the left ribs that filters blood. It can swell a little during the injections.
Commonly believed
What worries do donors have about the injections?
"The injections are a kind of chemotherapy."
They are not. G-CSF does not kill cells. It copies a signal your body already makes to produce white cells. Patients having chemotherapy are sometimes given it for the opposite reason, to help their counts recover.
"More pain means something has gone wrong."
Bone ache is expected and usually reflects busy marrow. What needs a same-day call is pain in a different place, especially the upper left belly or left shoulder tip.
"G-CSF can give the donor blood cancer later."
This question has been studied in large groups of healthy donors followed for years. So far those studies have not shown a clear increase in risk. Research is still going on, and your donor team will talk you through what is known.
"If I feel bad, I can just skip a day."
Skipping can mean too few cells to collect, which may delay the patient's transplant. Call the team instead. They can often help you manage the ache.
Questions donors ask
Common questions about G-CSF injections
How soon does the bone pain go away?
For most donors the ache starts easing once the injections stop, and has gone within a few days of collection. If it is still strong a week later, or is getting worse rather than better, call the donor team so they can check you. Do not simply wait it out.
Can I go to work during the injection days?
Many donors with desk jobs keep working, at least for the first few days. Physical jobs are harder, because the ache and tiredness build. Ask for lighter duties, and keep collection day free. The centre can usually give you a letter for your employer.
Can I take my usual painkiller?
Ask the donor team before you take anything. Some painkillers affect bleeding, and your platelets can drop after collection. Tell them about every medicine and supplement you use, including ayurvedic or herbal products, so they can tell you what is safe during these days.
Can I give the injections myself at home?
Some centres allow it after a nurse has shown you or a family member how. Others ask you to come in each day. Keep the medicine stored exactly as instructed, often in a fridge, and never change the timing or amount without speaking to the team.
What if I get a fever?
A slight feverish feeling is common. A real fever, shivering or feeling very unwell should be reported to the donor team the same day. They need to rule out an infection, which could affect both your safety and the timing of the collection.
Is G-CSF safe if I have a health condition?
That is exactly what the donor health check is for. Some conditions, including certain blood, heart and autoimmune problems, can make G-CSF unsafe. Be completely open at the check. Being turned down protects you, and the patient's team will look for another option.
Can I drink alcohol or smoke during the injections?
It is wise to avoid alcohol, because it adds to dehydration and headache. Smoking is best avoided too. If you are not sure how to manage without, speak to the team honestly rather than hiding it. They are there to keep you well.
Can women who are pregnant or breastfeeding have G-CSF?
Donors who are pregnant are generally not asked to donate, and a pregnancy test is usually part of the health check. If you are breastfeeding or planning a pregnancy, tell the donor doctor early so they can discuss whether and when donating is suitable for you.
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Sources
- American Cancer Society — Stem cell transplant donors
- NHS — Stem cell and bone marrow transplants
- Cancer Research UK — Cancer drugs A to Z
- National Cancer Institute — Stem Cell Transplants in Cancer Treatment
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
What Stem Cell Donation Actually InvolvesEvery stage of the donor processRisks to the Donor: An Honest AccountThe rarer risks, set out plainlyRecovery After Donating Stem CellsWhat to expect once collection is overDonor Eligibility: Age, Weight and Health ConditionsHealth conditions that affect donating
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