Medications
Filgrastim (Neupogen)
An injection (Neupogen) of a lab-made copy of G-CSF, a natural signal that tells the bone marrow to make more neutrophils (infection-fighting white blood cells); it is used to lower infection risk during strong chemotherapy, after bone-marrow transplant, and in severe chronic neutropenia. Filgrastim biosimilars (Zarxio/filgrastim-sndz and others) are distinct RxNorm ingredients — filgrastim-sndz is gated in Batch 67.
How Medicare covers it
Part D (forms used at home, incl. self-injection where a plan lists it). Part B covers the clinician-given injection where the CMS Part B spending file carries it (HCPCS J1442 — see the Part B basis in this package). Part A during a covered inpatient stay.
| Coverage details | |
|---|---|
| Part B status | CMS Part B Spending by Drug HCPCS file (RY26, data through 2024) carries J1442 (injection, filgrastim (G-CSF), excludes biosimilars, 1 microgram): the clinician-given originator path has a Part B basis. Biosimilar rows (Q5101 filgrastim-sndz, Q5110 filgrastim-aafi, Q5125 filgrastim-ayow) belong to the biosimilar ingredients and are explicitly NOT matched here (the Q5101 row is carried in the gated filgrastim-sndz package). |
| Medicare Advantage | Most Medicare Advantage plans that include drug coverage (MAPD plans) use the same formulary-and-tier system; the plan's own drug list decides coverage and copay — check the plan's formulary. |
| Medicare Supplement (Medigap) | Medicare Supplement (Medigap) plans sold today do not include prescription drug coverage; drug coverage comes from Part D or an MAPD plan. |
What it treats
Low neutrophil counts (a type of white blood cell) in several settings: to lower the chance of infection with fever in people with nonmyeloid cancers getting chemotherapy that strongly lowers blood counts; to shorten neutrophil recovery and fever after induction or consolidation chemotherapy for acute myeloid leukemia (AML); to shorten neutropenia after bone marrow transplant; to move the patient's own blood-forming stem cells into the blood so they can be collected by leukapheresis; for long-term use in symptomatic severe chronic neutropenia (congenital, cyclic, or idiopathic); and to increase survival in people acutely exposed to radiation doses that damage bone marrow. Brand name Neupogen (originator filgrastim).
What it is for, in depth
Neupogen (filgrastim) is an injection that helps the bone marrow make more neutrophils, the white blood cells that fight infection, when those counts are dangerously low. It is prescribed for people whose counts drop from cancer chemotherapy or a bone marrow transplant, for people born with or who develop severe chronic neutropenia, to collect a patient's own stem cells before a transplant, and to help people survive a large radiation exposure that damages the bone marrow. In the treatment path it is a support medicine given around chemotherapy or transplant care, not a cancer treatment itself. It comes as a clear liquid in single-dose vials (300 mcg/mL and 480 mcg/1.6 mL) and single-dose prefilled syringes (300 mcg/0.5 mL and 480 mcg/0.8 mL), given under the skin or into a vein.
How it works
Filgrastim is a man-made form of G-CSF (granulocyte colony-stimulating factor), a protein the body makes. G-CSF binds to receptors on blood-forming cells in the bone marrow and pushes them to make, mature, and release more neutrophils, the white blood cells that fight bacterial infection. It acts mainly on the neutrophil line and has minimal direct effect on other blood cell types.
How it is taken
Given as an injection under the skin (subcutaneous) or into a vein (short 15- to 30-minute infusion or continuous infusion), with the dose based on body weight and the reason for use. For chemotherapy support the starting dose is 5 mcg/kg once a day, started at least 24 hours after chemotherapy and never within 24 hours before it, and continued daily for up to 2 weeks or until neutrophil counts recover. Bone marrow transplant and stem cell collection doses are 10 mcg/kg/day; severe chronic neutropenia starting doses are 6 mcg/kg twice a day for congenital neutropenia and 5 mcg/kg once a day for cyclic or idiopathic neutropenia; the radiation-exposure dose is 10 mcg/kg/day under the skin.
Common side effects
The most common side effects depend on the reason for use. In people getting chemotherapy for nonmyeloid cancers, effects seen at least 5% more often than with placebo included fever, pain, rash, cough, and shortness of breath; in AML, pain, nosebleed, and rash; after bone marrow transplant, rash; during stem cell collection, bone pain, fever, and headache; and in severe chronic neutropenia, pain, anemia, nosebleed, diarrhea, reduced sensation, and hair loss.
Serious warnings
Neupogen can cause splenic rupture, which can be fatal — report left upper belly or shoulder pain right away. Other serious risks in the label are acute respiratory distress syndrome (ARDS), serious allergic reactions including anaphylaxis, severe and sometimes fatal sickle cell crises in people with sickle cell disorders, kidney inflammation (glomerulonephritis), bleeding into the lungs in stem cell donors, capillary leak syndrome, very high white blood cell counts, low platelets, skin vasculitis, and inflammation of large and medium arteries. In severe chronic neutropenia, myelodysplastic syndrome (MDS) and AML have occurred, and MDS/AML have also been linked to Neupogen used with chemotherapy and/or radiation in breast and lung cancer, so patients are monitored for these.
Who should be careful
Neupogen must not be used by people with a history of serious allergic reactions to human granulocyte colony-stimulating factors such as filgrastim or pegfilgrastim. People with sickle cell disorders, breathing problems, kidney problems, or spleen pain need close watching, and blood counts (CBC and platelets) are checked regularly during treatment. For severe chronic neutropenia, the diagnosis should be confirmed with blood counts and bone marrow testing before long-term treatment starts.
Major interactions
The Neupogen label has no Drug Interactions section and names no specific interacting drugs. It does warn that using Neupogen at the same time as chemotherapy or radiation therapy is not recommended, and that Neupogen should not be given within 24 hours before or 24 hours after cytotoxic chemotherapy, because rapidly dividing myeloid cells may be extra sensitive to the chemotherapy.
Cost and saving notes
If this drug is covered under your Medicare Part D plan and the cost is high, you can ask your plan for a tier exception to pay a lower cost share. If you have limited income, Extra Help (the Part D Low-Income Subsidy) can lower your Part D premiums and drug costs. In 2027, your total yearly out-of-pocket spending on covered Part D drugs is capped at $2,400, and you can spread those costs out in monthly payments through the Medicare Prescription Payment Plan.
Why it is in its tier
Filgrastim (Neupogen) sits on Tier 5 in 84.62% of the plans that list it (55 of 65 listing plans). Tier 5 is the specialty tier — instead of a flat copay, patients usually pay a percentage of the drug's cost (coinsurance), which is why specialty drugs feel expensive even with coverage. The data-visible drivers: It is a brand-only product with no generic version in the formulary data, and the CMS dashboard puts its average Part D spending at about $6,945 per beneficiary for 2024 — a high-cost drug, which matches where plans place it. Only 1.18% of Part D plans list it at all, so many readers will find their plan does not list it and covers a similar drug instead. The tier shown is the most common one; individual plans vary.
Sources
- NEUPOGEN (FILGRASTIM) INJECTION, SOLUTION [AMGEN, INC] — DailyMed
- MedlinePlus — National Library of Medicine
- MedlinePlus — Filgrastim Injection
What official patient guides say
Filgrastim is an injection, not a pill, so food does not affect it and you can keep your normal diet. It is given once or twice a day, either under the skin or into a vein, depending on why you need it. A nurse may give it, or you or a caregiver may be trained to inject it under the skin at home. If you inject at home, do not shake the vial or syringe, check that the liquid is not cloudy, discolored, foamy, or full of particles, and use each vial or syringe only once, putting used needles in a puncture-resistant container. If you forget a home dose, MedlinePlus does not give a catch-up rule — talk to your doctor about what to do instead of guessing or doubling up. Store filgrastim in the refrigerator in its original container, out of children's reach; some products may sit at room temperature for up to 24 hours away from sunlight, but do not use a vial or syringe that has been frozen twice. Bone and joint pain are common, and regular lab checks are part of the routine.
Part D formulary coverage
| Formulary summary | |
|---|---|
| Most common tier | 5 |
| Plans listing this drug | 65 |
| Total Part D plans | 5495 |
| Share of plans listing it | 1.18 |
| Formularies listing it | 9 |
| Tier | Plans |
|---|---|
| Tier 1 | 10 plans |
| Tier 5 | 55 plans |
Source: CMS Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files — Monthly file 2026-10-15 (plan year 2027), file 2027_20261008.zip (data.cms.gov dataset ed1496ea-23e7-41f1-9292-172fa842ccfb): basic drugs formulary file + plan information file, both dated 20261031 inside the zip; downloaded and aggregated 2026-10-30. Medication RxCUI sets resolved through the NLM RxNav (RxNorm) API.
What you pay
| With Medicare Part D | |
|---|---|
| Most common tier | Tier 5 |
| Typical coinsurance | 31.0% of the price |
| Based on | 53 plans that cover this drug · 2027 plan year |
Without insurance, the cash benchmark is $304.0908 per unit (NEUPOGEN 300 MCG/ML VIAL) — about $9122.72 for 30 units. NADAC benchmark — the average price pharmacies pay (CMS, as of 2026-11-04). Pharmacy shelf prices vary.
A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.
Sources: CMS Plan Benefit Package + formulary data; CMS NADAC · Checked 2026-11-08
Similar medications
Other medications in the same FDA pharmacologic class (Leukocyte Growth Factor):
Read next
Part D spending averages (2024)
| Brand name | Generic name | Total claims 2024 | Total spending 2024 | Total beneficiaries 2024 | Rank by beneficiaries 2024 |
|---|---|---|---|---|---|
| Neupogen | Filgrastim | 2908 | 7.20875e+06 | 1038 | 1804 |
Source: CMS Medicare Part D Spending by Drug (Drug Spending Dashboard), release RY26 P04 V10, data through 2024 (DSD_PTD_RY26_P04_V10_DY24_BGM.csv), downloaded 2026-10-30
Companies covering this drug
65 plans from 11 companies list this drug on a formulary for 2027. Search by company or plan name, or filter by tier. Cost sharing is the plan's published amount for this drug's tier in the initial coverage stage (1-month retail supply), where the plan publishes it; a blank means the plan does not publish it.
| Company | Plan | Tier | Copay | Coinsurance |
|---|
A tier is not a price; what you pay depends on your plan, pharmacy, and benefit stage; Extra Help or Medicaid can lower it further.
Coverage and costs change. Drug lists (formularies), tiers, and copays can change during the year and differ by plan. Always check with your insurance company or plan directly to confirm what is covered and what you will pay.
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