Tests Before Surgery: What Patients Need to Know

Being told that you need surgery can bring up many questions. You may want to know how the procedure will be performed, how long recovery might take and, of course, whether you are medically ready for the operation.

Before many planned surgeries, doctors recommend a preoperative assessment. This may include blood tests, an ECG, urine tests or other investigations, depending on the procedure and your medical history.

These assessments help the medical team understand your health, identify concerns that may need attention and plan your care before, during and after surgery.

Why Are Tests Done Before Surgery?

Preoperative tests are not simply a routine checklist that every patient must complete. They help answer specific questions about a person’s health and suitability for the planned procedure.

Your doctor may recommend investigations to:

• Check for medical conditions that could affect surgery.
• Assess blood counts and other relevant laboratory values.
• Evaluate heart or lung health when indicated.
• Review kidney function, blood glucose or other measurements relevant to your condition.
• Identify issues that may affect anaesthesia or recovery.
• Plan additional precautions or treatment if needed.

Not every patient needs every test. The recommended investigations depend on the type of surgery, your age, symptoms, existing medical conditions and the findings from your clinical assessment.

Which Tests May Be Required Before Surgery?

1. Complete Blood Count (CBC)

A complete blood count measures components of the blood, including red blood cells, white blood cells and platelets.

It may be recommended when the results could affect surgical planning. For example, a low haemoglobin level may suggest anaemia, while platelet levels can be relevant to blood clotting.

Whether a CBC is necessary depends on the planned operation and the patient’s medical history.

2. Blood Sugar Testing

Blood glucose testing may be recommended for patients with diabetes, symptoms suggesting high blood sugar or other relevant risk factors.

If a patient has diabetes, the medical team may review glucose control and plan how to manage diabetes medicines around the procedure.

Good preparation helps the team make an appropriate perioperative plan, but individual instructions should come from the treating clinician.

3. Kidney Function Tests

Kidney function tests may include measurements such as creatinine and estimated glomerular filtration rate (eGFR).

These tests may be relevant when a patient has known kidney disease, certain medical conditions or is undergoing a procedure where kidney function could influence treatment decisions.

The results can help clinicians review medication choices and other aspects of care.

4. Blood Clotting Tests

Tests such as PT/INR or aPTT measure aspects of the blood’s clotting process.

They may be appropriate for patients with a history of bleeding, certain liver conditions, relevant clotting disorders or specific medicines that affect coagulation.

These tests are not automatically required for every patient. Your doctor will decide whether they are useful for your situation.

5. Urine Tests

A urine test may be recommended when symptoms, medical history or the planned procedure make it relevant.

Depending on the test, it can help assess signs of a urinary infection, blood in the urine or other abnormalities.

If you have burning during urination, fever, blood in the urine or other urinary symptoms before surgery, inform your medical team.

6. Electrocardiogram (ECG)

An electrocardiogram records the electrical activity of the heart.

An ECG may be recommended for patients with relevant heart conditions, symptoms or risk factors, or when the type of surgery and clinical assessment indicate that it is needed.

An ECG is not necessary for every person undergoing every operation. The decision depends on individual risk and the planned procedure.

7. Chest X-ray

A chest X-ray may be useful when there is a specific clinical reason to assess the lungs or chest.

For example, a doctor may consider it when a patient has relevant respiratory or cardiac symptoms or a medical history that makes the result important to planning.

A chest X-ray is not routinely required for all patients before surgery.

8. Other Tests Based on Your Health

Some patients may need additional investigations depending on their diagnosis, existing conditions or the planned operation.

These may include:

• Ultrasound or other imaging
• Echocardiography in selected cases
• Pulmonary function tests when indicated
• Pregnancy testing when relevant and appropriate
• Blood group and compatibility testing for procedures where transfusion may be needed

Your surgeon and anaesthesia team will determine which investigations are appropriate. You should not arrange unnecessary tests without discussing them with your healthcare provider.

What Is a Pre-Anaesthesia Assessment?

A pre-anaesthesia assessment is an important part of preparing for many operations.

An anaesthesiologist reviews your medical history, current health, previous anaesthesia experiences, allergies and medicines. They may also examine you and review the results of relevant investigations.

During this assessment, be prepared to discuss:

• Previous surgeries and any complications
• Allergies or reactions to medicines
• Heart, lung, kidney or other medical conditions
• Diabetes, high blood pressure or sleep apnoea
• Prescription medicines, over-the-counter drugs and supplements
• Smoking, alcohol use or other relevant habits
• Any previous problems with anaesthesia

This conversation helps the team plan anaesthesia and monitoring based on your individual needs.

Do All Patients Need the Same Preoperative Tests?

No. Testing should be guided by the person’s health and the type of operation.

For example, a healthy person undergoing a minor procedure may need fewer investigations than someone having major surgery who also has diabetes or heart disease.

Some tests may be required because of the specific procedure, while others may only be needed if symptoms or medical history indicate a concern.

A useful question to ask your doctor is: “What is this test checking, and how could the result affect my surgery?”

Understanding the reason for each investigation can make the preparation process clearer.

How Should You Prepare for Tests Before Surgery?

Your hospital or doctor will provide instructions based on the tests you need. A few practical steps can help you prepare.

Follow Fasting Instructions Carefully

Some blood tests or procedures may require fasting, but many tests do not.

Do not assume that you must stop eating and drinking before every blood test. Follow the specific instructions provided by your medical team.

Bring Your Previous Reports

Carry recent laboratory results, imaging reports, discharge summaries and records of previous surgeries when available. Your doctor can decide whether earlier results are still relevant or need repeating.

Share Your Medication List

Write down all prescription medicines, non-prescription medicines, vitamins and supplements you take.

Do not stop blood thinners, diabetes medicines or other prescribed medication on your own. Ask your surgeon or anaesthesiologist for specific instructions.

Tell the Team About New Symptoms

Inform your medical team if you develop fever, cough, breathing difficulties, chest pain, a new infection or another significant change in health before the scheduled operation.

The team can decide whether any further assessment or change in timing is needed.

What Happens If a Test Result Is Abnormal?

An abnormal result does not automatically mean that surgery will be cancelled.

The medical team will interpret the finding in context. Depending on the result, they may recommend repeating a test, conducting further investigations, adjusting medication, treating an underlying problem or modifying the surgical plan.

In some situations, it may be appropriate to postpone a planned operation until a medical concern has been assessed or managed. In other situations, the finding may not affect the procedure.

The decision depends on the result, the urgency of surgery and the balance of potential risks and benefits.

What Should You Tell Your Doctor Before Surgery?

Along with completing the recommended tests, give your doctor a clear picture of your health.

Mention any:

• Previous reactions to anaesthesia
• Allergies to medicines or other substances
• Bleeding or clotting problems
• Heart or lung conditions
• Diabetes or kidney disease
• Recent infections or fever
• Pregnancy possibility, when relevant
• Medicines that affect blood clotting
• Implants, devices or other relevant medical history

Even if something seems unrelated to your planned operation, it may be important for the team to know.

Frequently Asked Questions

Are blood tests necessary before every surgery?

No. Blood tests are selected according to the planned operation, the patient’s medical history and the clinical assessment. Some procedures require little testing, while others need more detailed investigations.

Is an ECG compulsory before surgery?

An ECG is not required for every patient. It may be recommended based on symptoms, heart history, other risk factors and the type of surgery.

Why might a doctor request a chest X-ray before surgery?

A chest X-ray may be requested when there is a specific reason to assess the chest or lungs. It is not routinely needed for every otherwise healthy patient.

How long before surgery should tests be completed?

Timing depends on the operation, the tests required and the hospital’s instructions. Some results may remain useful for a period, while others may need repeating if your health changes or the results are no longer current.

Can surgery be postponed because of test results?

Yes, in some cases. If a result reveals a concern that could affect the procedure or anaesthesia, the team may recommend further assessment or treatment before proceeding. An abnormal result does not automatically mean cancellation.

Should I take my regular medicines on the day of surgery?

That depends on the medicine and the procedure. Ask your treating doctor or anaesthesiologist for individual instructions. Do not independently stop or change prescribed medication.

Final Thoughts

Tests before surgery help doctors make decisions based on the patient’s health rather than relying on a one-size-fits-all checklist.

Your preoperative assessment may include blood tests, an ECG, urine testing or other investigations, but the exact requirements vary. Sharing your medical history, bringing previous reports and following the hospital’s instructions can help make the preparation process more organised.

If you are scheduled for surgery, ask your surgeon which tests you need, why they are recommended and how to prepare. Clear communication with your healthcare team is an important part of preparing for an operation.