Hematologist
CION Cancer Clinics
Transplant day zero: what actually happens | CION Cancer Clinics
On day zero, the stem cells are dripped into your central line, much like a blood transfusion. There is no operation, you stay awake in your room, and a nurse watches closely throughout. The cells find their own way into the bone marrow. Most reactions are mild, and a garlic smell is expected with frozen cells. This page walks through the day and what to tell the nurse. At CION Cancer Clinics, our haematology team assesses whether a transplant or CAR-T fits your situation and coordinates care with qualified centres.
BP
Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
- What actually happens on transplant day zero?
- What happens from morning until the drip is finished?
- Does the day differ depending on where the cells come from?
- What do families often misunderstand about day zero?
- Which changes are expected, and which need the nurse now?
- What can day zero not tell you?
- Common questions about transplant day zero
The short answer
What actually happens on transplant day zero?
On day zero the stem cells are dripped into your central line, much like a blood transfusion. There is no operation and no anaesthetic; you stay in your room, awake, and the drip itself often takes less time than families expect.
Why it is called day zero
Transplant teams count everything from the day the cells go in. The conditioning days before it are minus days. Every day after is a plus day, so your chart may say day plus seven or day plus fourteen. This makes it easy to compare your recovery with what the team expects.
Where the cells go after the drip
The stem cells travel through the blood and find their own way into the bone marrow, the soft tissue inside the bones where blood is made. Nobody has to place them there. Over the following weeks they settle in and start making new blood cells. That later stage is called engraftment.
Why the day can feel like an anticlimax
After weeks of tests and a hard conditioning, many families expect a dramatic moment. Day zero is usually quiet. The hard part, when counts fall to their lowest, generally comes in the days after it. Some families still mark the day as a new birthday.
Through the day
What happens from morning until the drip is finished?
-
The cells arrive
Donor cells may arrive fresh from the collection centre, sometimes the same day. Your own cells, or donor cells stored earlier, are brought frozen and thawed in a warm water bath at the bedside.
-
Checks and pre-medicines
Two staff check the bag label against your wristband and records. You may be given medicines to reduce the chance of a reaction, such as an antihistamine and anti-sickness medicine.
-
The drip
The bag is connected to your central line. A nurse stays close and checks your pulse, blood pressure, temperature and breathing often. You can talk, rest or have family in the room if the unit allows it.
-
Watching afterwards
Checks continue for some hours after the bag is empty. Most people have no serious reaction. Any that do occur are usually mild and managed quickly.
-
The days that follow
Counts keep falling. Fever, a sore mouth and loose motions are common in this stretch, and you stay in the protected room until the new cells start working.
Not sure whether this applies to you?
Ask an oncologistDifferent sources
Does the day differ depending on where the cells come from?
The drip looks similar, but the source changes a few details you may notice.
Your own cells
In an autologous transplant, your stem cells were collected and frozen earlier. They are thawed and given in one or more bags.
You may notice
- A strong garlic or sweetcorn smell in the room
- A strange taste in the mouth
Donor blood stem cells
Collected from a donor's bloodstream, often fresh. The bag looks like a blood transfusion and usually runs without much fuss.
If the blood groups differ, extra steps may be taken to prevent a reaction.Donor bone marrow
Taken from the donor's hip bone under anaesthetic. The bag is larger, so the drip may take longer, and the team watches fluid balance closely.
Cord blood
Stem cells from umbilical cord blood donated at a birth. The volume is small and the drip is often short. Counts may take longer to recover.
!
Tell the nurse straight away during the drip
Say so at once if you feel your chest tighten, find it hard to breathe, feel faint, get a rash or itching, shiver, or feel your heart racing. The nurse can slow or pause the drip and treat the reaction within minutes. Families should press the call bell rather than wait for a check if the patient seems unwell.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Commonly believed
What do families often misunderstand about day zero?
"A transplant means they will operate on the bones."
There is no operation for the patient. The cells go in through the central line and find their own way into the marrow. Only a bone marrow donor has a procedure, and that is done on the donor, not on you.
"Once the cells are in, the danger is over."
Day zero is the start of the most fragile stretch. Counts are falling and infection risk is at its highest over the next weeks. The protected room, hand washing and visitor rules matter most now.
"That smell means something has gone wrong."
Frozen cells are stored with a preservative that gives the breath and skin a garlic or sweetcorn smell. It is expected and fades on its own over a day or two. It does not mean infection or harm.
"Red urine after the drip means bleeding."
Broken-down red cells from the bag can colour the urine pink or red for a short time. It is usually harmless. Still tell the nurse, so the team can check whether it is this or true bleeding.
Normal or not
Which changes are expected, and which need the nurse now?
Usually expected
Tell the nurse at once
A garlic or sweetcorn smell on the breath
Tight chest or trouble breathing
A strange taste; sucking a sweet can help
A rash, swollen lips or itching
Feeling a little sick or flushed
Shivering, fever or feeling faint
Pink urine for a short while
Very little urine, or blood clots in it
Being straight with you
What can day zero not tell you?
How the drip goes says very little about how the transplant will work. A smooth day zero does not promise easy weeks ahead, and a reaction during the drip does not mean the cells will fail. The signs that matter come later, when the blood counts start to rise.
What the team will be watching next
Daily blood counts, temperature, weight, fluid balance, liver tests and how well you are eating and drinking. These guide transfusions, antibiotics and support medicines. Ask the team which numbers they are watching for you, and what would count as progress.
What to ask the transplant centre
How many bags will I receive, and are they fresh or frozen? Who will be with me during the drip? Can a family member be present? What happens if I react? Asking before the day makes it far less frightening.
CION's haematology team reviews cases, presents them at a tumour board and coordinates referral with qualified transplant centres. We can help you prepare for the admission.Questions we are asked
Common questions about transplant day zero
How long does the stem cell infusion take?
It depends on the number and size of the bags. A small bag of cord blood or thawed cells may run quite quickly, while a large bag of donor bone marrow takes longer. Ask the nurse on the morning how long your drip is expected to run, so the family can plan.
Does the stem cell infusion hurt?
The drip itself should not hurt, because it goes through the central line already in place. Some people feel cold, flushed, a little sick or notice a strange taste. Tell the nurse about anything that feels wrong, even if it seems small, so it can be checked.
Can family be in the room on day zero?
Many units allow one healthy attendant, following the usual hand washing and mask rules. Some allow a short prayer or quiet moment before the drip. Rules differ between centres, so ask ahead. Anyone with a cold, cough or fever should stay away.
What if my body rejects the cells?
Rejection does not happen during the drip. Whether the cells take hold becomes clear over the following weeks, as counts start to rise. Graft failure is uncommon, and the team has plans if it happens. Ask them how they will know the cells are working.
Why does the room smell of garlic?
Frozen stem cells are stored with a preservative that leaves the body through the breath and skin. It smells like garlic or sweetcorn to most people. It is harmless and fades over a day or two. Some find sucking a sweet helps with the taste.
Can I eat and drink during the infusion?
Usually yes, if you feel like it, unless your team has told you otherwise. Many people do not feel hungry. Sips of water and light food are fine. Follow the ward's food safety rules, because your immune defence is very low at this point.
When will we know if the transplant has worked?
The first sign is the white cell count starting to rise, which usually takes a few weeks. Whether the disease stays away is judged over months, with bone marrow tests and blood tests. Your team will tell you which tests are planned and when.
Is day zero the same for a second transplant?
The drip itself is usually similar. The conditioning before it, and the risks after it, may be different because of earlier treatment. Your team will explain what will be different this time and what they will watch more closely.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Sources
- NHS — Stem cell and bone marrow transplants
- Cancer Research UK — Bone marrow and stem cell transplants
- National Cancer Institute — Stem Cell Transplants in Cancer Treatment
- American Cancer Society — Stem Cell Transplant for Cancer
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
Conditioning Chemotherapy: What It Does and WhyThe treatment in the days before day zeroEngraftment: Waiting for Counts to RecoverWhat happens as the new cells start workingThe Transplant Isolation Room: Daily Life InsideThe room you stay in after the dripInfection During the Neutropenic Phase of TransplantThe biggest risk in the weeks after
Talk to us
Preparing for a transplant?
Share the reports with us. CION's haematology team will review the case, discuss it at a tumour board and help you prepare questions for the transplant centre.