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Blood tests before cancer surgery, in plain words | CION Cancer Clinics
Blood tests before cancer surgery usually include a complete blood count, kidney and liver tests, sugar, clotting, blood group and an infection screen. They check whether your body is ready for anaesthesia and healing, and find problems that can often be fixed first. They do not show whether the cancer has spread. This page explains each test and what an abnormal result usually leads to. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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On this page
- Which blood tests are done before cancer surgery?
- What does each blood test check?
- What do the words on your blood report mean?
- How do blood tests fit into the weeks before surgery?
- What usually happens when a blood test is abnormal?
- What do families often believe about pre-surgery blood tests?
- How do your medicines affect blood tests before surgery?
- Common questions about blood tests before cancer surgery
The short answer
Which blood tests are done before cancer surgery?
Most people have a complete blood count, kidney and liver tests, a sugar test, a clotting test, a blood group and an infection screen. Together they show whether your blood and organs are ready for anaesthesia, surgery and healing.
What these tests are for
They look for problems that make surgery less safe and can often be fixed first. A low haemoglobin, high sugar, poor kidney function or slow clotting all change how the team prepares. Finding them early gives time to correct them without a last-minute cancellation.
What they are not for
These tests do not show where the cancer is or whether it has spread. That comes from your biopsy and scans. A normal blood report is good news for your fitness. It is not a statement about the cancer itself.
Why some tests are repeated
Results can change over a few weeks, especially after chemotherapy, a long wait for the operation date or a new illness. The anaesthetist wants results that reflect your body close to the day of surgery. If you have recent reports from another lab, bring them and ask whether they can be used.
What this page cannot tell you
It cannot interpret your own report. Lab ranges differ between laboratories, and a value flagged high or low may or may not matter for your operation. Your anaesthetist and surgeon read the results together with your history, medicines and the size of the surgery.
The usual panels
What does each blood test check?
The request slip can list many names. Most fit into these groups.
Complete blood count
Haemoglobin, white cells and platelets. It shows whether you can cope with blood loss, fight infection and stop bleeding.
Kidney tests
Creatinine, urea and salts such as sodium and potassium. Kidneys clear anaesthetic drugs and balance fluids after surgery.
Liver tests
Bilirubin, liver enzymes and albumin. Albumin also hints at nutrition, which affects wound healing.
Sugar tests
A fasting or random sugar, and often HbA1c, which shows sugar control over the past few months.
Clotting and blood group
How quickly blood clots, and your blood group, so matched blood is ready if needed.
Often listed as
- PT/INR and aPTT
- Grouping and cross-matching
Infection screen
Hepatitis B, hepatitis C and HIV. These are routine and do not stop cancer surgery if positive.
Not sure whether this applies to you?
Ask an oncologistOn your report
What do the words on your blood report mean?
- Haemoglobin (Hb)
- The part of red cells that carries oxygen. A low level makes you tired and breathless, and is often corrected before surgery.
- Platelets
- Tiny cells that help blood clot. Low levels can increase bleeding.
- Creatinine and eGFR
- Measures of kidney function. A raised creatinine or low eGFR means the kidneys are working less well.
- HbA1c
- Average blood sugar over recent months. It shows how well diabetes is controlled.
- INR
- How long blood takes to clot. It is raised by warfarin and some liver problems.
- Albumin
- A protein made by the liver. Low levels often point to poor nutrition or illness.
From slip to surgery
How do blood tests fit into the weeks before surgery?
-
The request slip
Your surgeon or anaesthetist lists the tests. Ask which ones need fasting, so all the samples can be taken in one visit.
-
The samples
Blood is taken from a vein in your arm, usually in a few small tubes. Drink water beforehand unless told otherwise, as it makes the vein easier to find.
-
The reports
Most results come back quickly. Some, such as certain infection tests, take longer. Collect every report and keep them together.
-
Review and correction
The anaesthetist reads the results at your check-up. If something needs fixing, such as sugar or haemoglobin, treatment starts and the test is repeated.
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Final samples near the date
A fresh blood count and a cross-match are often taken close to the operation, so matched blood is ready if needed.
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If a result is off
What usually happens when a blood test is abnormal?
The finding
What the team often does
Low haemoglobin
Looks for the cause and may give iron or a transfusion
High sugar or high HbA1c
Adjusts diabetes medicines, sometimes with a diabetes doctor
Raised creatinine
Checks fluids and medicines, and plans kidney-safe drugs
Raised INR or low platelets
Finds the reason and plans how to reduce bleeding
Low albumin
Arranges nutrition support before the operation
Commonly believed
What do families often believe about pre-surgery blood tests?
"Taking blood will make him weaker before surgery."
The amount taken is small, and the body replaces it quickly. The information from those tubes helps the team keep him safer during the operation.
"We should arrange our own blood donors now."
Ask the hospital first. Blood banks have their own rules, and many operations do not need a transfusion. The team will tell you if donors are needed, and when.
"A red mark on the report means surgery is off."
Many flagged values are slightly outside the lab range and do not matter for surgery. Others are corrected first. The team decides which is which, so bring the report and ask.
"A tumour marker test will show if surgery is safe."
Tumour markers such as CEA or CA-125 relate to certain cancers. They are not fitness tests, and a normal value does not rule out cancer or make surgery safer.
Medicines and results
How do your medicines affect blood tests before surgery?
Several common medicines change blood results, so the team needs a complete list. Bring the strips or prescriptions to every visit.
Blood thinners
Warfarin raises the INR. Aspirin, clopidogrel and newer blood thinners affect bleeding even when routine tests look normal. The surgeon, anaesthetist and prescribing doctor decide if and when any of these are paused. Never stop one on your own, as that can cause a stroke or heart attack.
Diabetes medicines and steroids
Metformin, insulin and other diabetes medicines need a plan around fasting and surgery. Steroids can raise sugar. The team tells you what to take on the morning of the operation.
After chemotherapy
Chemotherapy can lower blood counts and affect the kidneys or liver. Counts usually recover, and tests are repeated before the date is fixed. Tell the team the names of the drugs you received.
Herbal and home remedies
Ayurvedic, herbal and homeopathic products can also affect bleeding, sugar or the liver. Many families do not think to mention them. Bring the bottles or packets to the check-up, and say honestly what is being taken. The team is asking to keep you safe, not to judge.
Questions we are asked
Common questions about blood tests before cancer surgery
Do I need to fast for blood tests before surgery?
Only for some tests, such as a fasting sugar or a lipid profile. Most others can be done after food. Ask when the slip is written. If you have diabetes, ask how to manage your medicines while fasting, so your sugar does not drop too low.
Why is my blood group tested again if I already know it?
Blood banks must confirm your group themselves before giving blood, for your safety. A cross-match also checks that a particular unit of donor blood is compatible with yours. A card or an old report is not enough on its own.
My haemoglobin is low. Will the operation be delayed?
It may be, depending on how low it is and how urgent the surgery is. The team looks for the cause and may give iron tablets, an iron drip or a transfusion. Ask how long correction is likely to take and when the test will be repeated.
Can I get these tests done at a lab near home?
Often yes, especially if you live in a district and travel for each visit. Use a recognised lab and bring the original reports. Blood group and cross-match are usually repeated at the hospital doing the operation.
Why do I need an HIV test?
It is part of a routine infection screen before many operations. It helps the team protect you and the staff and plan any extra care you need. A positive result does not stop cancer surgery, and your results are kept confidential.
Will the blood tests show if the cancer has spread?
No. Routine pre-surgery blood tests check fitness, not cancer spread. Some liver results can be abnormal for many reasons, including a blocked bile duct. Your scans and biopsy answer the question of spread, and your surgeon explains those findings.
Are the tests repeated after the operation?
Usually, yes. Blood counts, kidney tests and salts are often checked in the days after surgery to watch for bleeding, infection or fluid problems. The frequency depends on the size of the operation and how you recover.
Are blood tests covered by Aarogyasri or insurance?
They are often covered when they are part of an approved cancer surgery plan. Aarogyasri, CGHS, ECHS, EHS and cashless insurance each have their own rules. Call the helpline with your card or policy details and the team can check your cover.
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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
Surgical Oncologist
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
Surgical Oncologist
Dr. Vajja Sandeep Kumar
MBBS, MS (General Surgery), DrNB (Surgical Oncology), FALS Oncology
Surgical Oncologist
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Sources
- NHS — Blood tests
- NICE — Routine preoperative tests for elective surgery (NG45)
- Cancer Research UK — Surgery for cancer
- National Cancer Institute — Surgery to Treat 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.
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