Medical Oncologist
Rituximab (MabThera) side effects
Rituximab Side Effects: — Timeline and When to Call
Rituximab is a monoclonal antibody that targets B-cells. It is generally better tolerated than many chemotherapy drugs, but it does cause specific side effects — most predictably during each infusion, and more gradually in the weeks and months that follow.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed August 2026
- Infusion reactions are the most common effect — Most occur during the first infusion. Your team gives pre-medications to reduce the risk and monitors you closely throughout each drip.
- Infection is the main ongoing concern — Rituximab depletes the cells that make antibodies. This risk continues for months after your last dose, not just during treatment.
- Most side effects are known and manageable — Your team has protocols ready for the most common reactions. Reporting symptoms early is what keeps them manageable.
- Timing tells you what to watch for — Different side effects appear at different points. Knowing the window helps you decide whether a new symptom needs a call today.
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Rituximab most commonly causes infusion reactions during or shortly after each drip, and an increased risk of infection in the weeks and months that follow. Most reactions are manageable. A few — breathing difficulty during infusion, fever with rigors, or signs of infection — need a call the same day they appear.
What side effects does rituximab cause, and when do they start?
| Side effect | How common | When it typically starts | Call today if |
|---|---|---|---|
| Infusion reaction (fever, chills, rash, throat tightness) | Very common on first infusion; less likely on later doses | During or within hours of each infusion | Difficulty breathing, dizziness or severe rash — alert the nurse immediately |
| Tiredness and low energy | Very common | After the first infusion onwards | Severe enough to prevent eating or drinking |
| Nausea | Common | During or shortly after infusion | You cannot keep fluids down |
| Low white blood cell count (neutropenia) | Common | Days to weeks after infusion | You develop a fever |
| Low platelet count | Common | Weeks after infusion; timing varies | Unusual bruising, bleeding gums or blood in urine |
| Infection | Common; risk increases as B-cell counts fall | Any time during treatment and months after | Fever, shaking chills, new cough or shortness of breath |
| Hepatitis B reactivation | Uncommon; mainly affects those who carried the virus before treatment | Weeks to months after starting | Jaundice, dark urine or upper abdominal pain |
| Late-onset low white cell count | Uncommon | Weeks to months after the last dose | Any fever in this period |
| Neurological changes (confusion, vision or speech problems) | Rare | Months into or after treatment | Go to emergency immediately — do not wait |
| Typically starts | Effects are most concentrated in the first months of treatment | Infusion reactions within hours of each drip; most other effects develop over weeks to months; late effects from several weeks after the last dose onward | Call whenever a new symptom worries you |
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Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
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Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
Surgical Oncologist
Surgical Oncologist
Dr. Vinay Mamidala
MBBS, MS(General Surgery), M.Ch(Surgical Oncology), FMAS, FARIS(Ongoing)
Surgical Oncologist
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Radiation Oncologist
Radiation Oncologist
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Dr. Mohammed Imran
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
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Does the infection risk stop when treatment ends?
No. Rituximab works by depleting B-cells, the immune cells that produce antibodies. This effect does not reverse on your last day of treatment.
B-cells take months to recover after rituximab ends. During this period, your body has fewer defences against certain bacteria, viruses and fungi, so infection remains a real risk even after you have finished your course.
This is why your team continues to monitor your blood counts after treatment ends, and why you should report any fever, new cough or feeling suddenly unwell — even in the weeks and months after your final infusion.
Did you know?
In a proportion of patients, B-cell counts remain low for six months or more after the last rituximab dose, according to data cited in European Medicines Agency prescribing information.
This is why your oncology team keeps monitoring blood counts after treatment ends, and why certain live vaccines are avoided during and for a period after your course.
Source: European Medicines Agency: Rituximab Summary of Product Characteristics
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Common questions
Frequently asked questions
Will I definitely get an infusion reaction?
Most people experience some degree of reaction during their first rituximab infusion — this is so common that your team will give pre-medications beforehand and monitor you closely throughout. Not everyone gets a severe reaction, and reactions tend to be milder or absent on later infusions. If a reaction develops, your team will slow or pause the drip and give medication. Most reactions settle with these measures.
Does rituximab cause hair loss?
Rituximab does not typically cause hair loss, which is one of the ways it differs from many chemotherapy drugs. It is a monoclonal antibody rather than a chemotherapy and works differently — it does not damage hair follicles in the same way. If you are receiving rituximab alongside chemotherapy, any hair loss is more likely to be from the chemotherapy component of your regimen. Ask your team which drugs in your plan are known to affect hair.
How long after my last dose am I still at risk of infection?
The infection risk continues for months after your last dose, not just while you are having treatment. Rituximab depletes B-cells, and those cells take months to recover — in a proportion of patients, counts remain low for six months or more. During this period, your immune system has fewer resources to fight certain infections. Your oncology team will monitor your blood counts and tell you when they are satisfied that recovery is on track.
Can I receive vaccines while on rituximab?
Live vaccines — which include some travel vaccines and the nasal flu spray — are generally avoided during and for a period after rituximab, because a depleted immune system may not handle a live virus safely. Inactivated vaccines, such as the injected flu vaccine, are usually still recommended, but timing matters: your body may respond less well when B-cell counts are low. Ask your team before having any vaccine, and tell any other healthcare provider that you are on or have recently completed rituximab.
Is rituximab given as a day stay or does it need a hospital admission?
Rituximab is administered as a day-care infusion — you come in for the drip and go home the same day. The first infusion takes the longest, because the rate is kept slow to reduce the risk of a reaction and you are monitored closely throughout. Later infusions, if you have tolerated the earlier ones well, may be given more quickly. You do not usually need to be admitted to a ward.