Medical Oncologist
Blood counts
Dizziness and fainting during chemotherapy
Most often a low haemoglobin, dehydration, or blood pressure dipping when you stand. All three are common, checkable and treatable, and the feeling is alarming out of proportion to what usually causes it. What actually harms people here is the fall — platelets may be low, so a knock bleeds and bruises more than it otherwise would.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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The short answer
Why do you feel dizzy during chemotherapy?
Most often because of a low haemoglobin, dehydration, or blood pressure dipping when you stand up. All three are common during treatment, all three are checkable, and all three are treatable. The feeling is alarming out of proportion to what usually causes it.
The commonest pattern by far is dizziness only on standing, settling within seconds. That points at blood pressure and fluids rather than anything sinister, and it responds to moving more slowly and drinking more.
The risk is the fall, not the dizziness
What actually harms people here is hitting the floor. Platelets may be low, so a fall bleeds and bruises more than it would otherwise, and a head injury during treatment is a serious matter. Most of this page is about preventing that.
Sit up first, then stand, then wait a moment before walking. That one habit prevents most falls.
!
Go to hospital the same day
Fainting, or losing consciousness even briefly · a fall, especially with a head injury or if on blood thinners · dizziness with chest pain or breathlessness · a racing or irregular heartbeat that will not settle · dizziness with a fever · confusion, slurred speech, weakness down one side, or a severe headache · the room spinning violently with vomiting · black tarry motions or any heavy bleeding. Go to the nearest emergency department and say clearly that the person is on chemotherapy.
Not sure whether this applies to you?
Ask an oncologistWhat it usually is
The common causes, and what each points to
Often more than one at once. Which applies decides what is actually done about it.
A low haemoglobin
Fewer red cells means less oxygen reaching the brain. Comes with tiredness that sleep does not fix, breathlessness on stairs and looking pale. Confirmed on the blood test taken before each cycle.
Ask
- What was my haemoglobin?
- Is it falling across cycles?
Not enough fluid
Extremely common, and the most fixable. Vomiting, loose motions, a sore mouth or simply not drinking enough all cause it. Judge it by urine — dark and scanty means you are short.
Cutting fluids to avoid the toilet is the commonest avoidable cause.Blood pressure dipping on standing
The classic pattern: fine sitting, dizzy on getting up, settles in seconds. Made worse by dehydration, by blood pressure tablets, and by lying down for long stretches.
Medicines
Anti-sickness medicines, painkillers, sleeping tablets and blood pressure tablets all cause it. Bring the full list to your oncologist — a timing change or a swap often solves it entirely.
Low blood sugar
Eating very little, or long gaps without food, particularly in anyone on diabetes medication. Steroids complicate this further by pushing sugar up and then letting it fall.
The inner ear, or something else
True spinning, where the room moves, is different from light-headedness and points elsewhere. So does dizziness with a headache, slurred speech or weakness — those need assessing the same day.
The part that matters most
Preventing the fall
Change position in stages
Sit up on the edge of the bed. Wait. Stand, holding something. Wait again. Then walk. Most falls happen in the first seconds of standing, and this single habit removes most of them.
Light and clear the route to the toilet
A night light, nothing on the floor, no loose mats, and slippers with a back rather than flapping chappals. Night-time trips are when falls happen.
Sit down for things you would stand for
Showering, dressing, chopping, brushing teeth. A plastic stool in the bathroom and one in the kitchen is the cheapest safety measure available.
Keep drinking
Steadily through the day, judged by urine rather than by thirst. If vomiting or loose motions are the reason, ask about rehydration solution rather than just water.
Do not lock the bathroom door
Unpleasant to think about and genuinely important, particularly for anyone living alone or prone to fainting. Keep a phone within reach of the bed and the bathroom.
If you feel it coming, get down
Sit or lie down where you are rather than trying to reach a chair. A controlled sit on the floor is far better than a fall from standing height.
Being useful
What to tell your team
The pattern matters more than the sensation. Dizziness only on standing, dizziness at rest, and the room spinning are three different complaints pointing in three different directions, and describing which one you have shortens the whole conversation.
The things worth saying
When it happens — on standing, walking, or sitting still. How long it lasts. Whether you have actually fainted or fallen. What else comes with it, particularly breathlessness, palpitations, headache or a fever. And what you have eaten and drunk that day.
Report every fall, even a minor one
People hide falls to avoid fuss, and during chemotherapy that is a bad trade. Low platelets mean bleeding under the skin and inside the head is more likely, and a knock that would have been nothing before treatment may not be now.
Take the medicine list
Including blood pressure tablets, diabetes medicines, painkillers and anything for sleep. Several of these cause dizziness in their own right, and the fix is frequently a timing change rather than anything new.
Do not stop a blood pressure tablet yourself because you feel dizzy. Ask — the dose may need adjusting, not stopping.Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Being straight with you
What this page cannot tell you
It cannot tell you what is causing yours. Dizziness is one of the least specific symptoms in medicine, and the causes here range from not drinking enough to problems with the heart or the brain. Blood pressure taken sitting and standing, blood tests and an examination are what separate them.
It also cannot tell you whether yours can wait. Dizziness only on standing, settling in seconds, with no other symptoms, can usually be raised at your next contact. Fainting, falling, or dizziness with chest pain, breathlessness, fever or neurological symptoms cannot.
What to do next
Start moving between positions in stages today. Put a stool in the bathroom and clear the route to the toilet. Drink steadily and judge it by urine. Take your full medicine list to the next appointment and describe the pattern rather than the feeling. And report any fall, however small.
Questions we are asked
Common questions about dizziness
I am only dizzy when I stand up. Is that serious?
That pattern is common and usually points at fluids, a low haemoglobin or blood pressure tablets rather than anything sinister. It is still worth reporting, because all three are treatable. The immediate priority is preventing a fall — stand in stages, and sit down if it comes on.
Should I stop my blood pressure tablets?
Not on your own. Blood pressure often falls during treatment because of weight loss and poor intake, so the dose that suited you before may now be too much — but that is an adjustment for your doctor to make. Take the tablets to your next appointment and describe when the dizziness happens.
I fell but I am fine. Do I need to mention it?
Yes, report every fall. Platelets may be low, so bleeding under the skin or inside the head is more likely than it would normally be, and a knock to the head matters more during treatment. Go in the same day if you hit your head or are on blood thinners.
Is the room spinning the same thing?
No, and the distinction is useful. True spinning, where the room moves around you, usually points at the inner ear rather than at blood pressure or haemoglobin. Say which one you have, because it sends the assessment in a completely different direction.
Could it be the anti-sickness medicine?
Quite possibly. Several cause drowsiness and light-headedness, and they are often taken for days after each cycle. Do not stop them, since uncontrolled sickness causes worse problems — but do mention the timing, as a change frequently helps.
Is it safe to drive?
Not while you are getting dizzy or feeling faint, and ask your team about driving generally during treatment. Several medicines affect concentration and reaction time. Many people stop during the difficult days of each cycle and drive again in the good week.
Will a transfusion stop it?
If a low haemoglobin is the cause, most people feel considerably steadier within a day. If dizziness continues afterwards, that is useful information — it means something else is contributing, most often fluids or medicines, and it should be looked at again.
My mother lives alone. What should we arrange?
A phone within reach of the bed and the bathroom, the bathroom door unlocked, a night light, loose mats removed, and someone calling at agreed times each day. If she is fainting or has fallen, living alone through treatment needs rethinking — raise it with the team.
Meet the Specialists
17+ senior cancer specialists. One panel for your case.
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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)
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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
Radiation Oncologist
Radiation Oncologist
Radiation Oncologist
Hematologist
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Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
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Sources
- Cancer Research UK — Cancer drugs side effects
- Macmillan Cancer Support — Low red blood cell count
- National Cancer Institute — Chemotherapy and You
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.
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