Preoperative Tests: Complete Checklist, Result Validity and Reasons for Postponement

Surgical procedures performed under anaesthesia, from tonsil removal to hip replacement, are preceded by laboratory tests. Their purpose is not simply to tick a box, but to assess whether your body can safely tolerate anaesthesia and blood loss, whether there is an undetected infection or blood clotting disorder, and to establish a baseline for postoperative monitoring. The list depends on the type of procedure, your age and any existing medical conditions, but the core investigations are similar. Below, we explain what a standard preoperative test panel includes, why each test matters, how long the results remain valid and how to avoid losing your surgery date because your results have expired. The final list of required tests is always determined by your surgeon or anaesthetist.

Standard preoperative test panel

Full blood count

Haemoglobin and haematocrit levels help determine whether a patient has sufficient reserves to tolerate blood loss during surgery. Preoperative anaemia increases the risk of blood transfusions and complications, so it is important to detect and treat it in advance (intravenous iron can take several weeks to produce an effect). The white blood cell count helps identify an ongoing infection, while the platelet count forms part of the assessment of blood clotting.

Blood group and Rh factor

Required before any procedure involving a risk of blood transfusion. Blood grouping must be performed twice using samples collected independently (or confirmed by an official document, such as a blood group identification card). A confirmed blood group result remains valid indefinitely, but the hospital may require its own confirmation.

Blood clotting: APTT, PT (INR) and fibrinogen

These tests help detect inherited and acquired blood clotting disorders and monitor patients taking anticoagulant medicines. INR is particularly important for people taking warfarin or acenocoumarol. Newer anticoagulants (rivaroxaban, apixaban and dabigatran) are not reliably assessed by routine coagulation tests and must be stopped according to a schedule established by your doctor, usually 24–72 hours before surgery.

Electrolytes: sodium and potassium

Abnormal Potassium (K) – laboratory test results increase the risk of heart rhythm disturbances during anaesthesia, and correcting potassium levels before surgery is relatively straightforward. Sodium (Na) – laboratory test and potassium measurements are particularly important for people taking diuretics or blood pressure medication and those with kidney disease.

Creatinine, eGFR and urea

Assessment of kidney function, including Creatinine – laboratory test and eGFR, helps determine appropriate doses of anaesthetic medicines, antibiotics, contrast agents and painkillers. Kidney impairment increases the risk of complications and requires adjustments to fluid management.

Glucose

Undiagnosed diabetes or poorly controlled blood glucose can delay wound healing and increase the risk of infection. Glucose – laboratory test is therefore important before surgery. People with diabetes should also have Glycated haemoglobin (HbA1c) measured. Many centres postpone elective procedures when HbA1c exceeds 8–8.5%.

Liver function tests: ALT, AST and bilirubin

The liver metabolises anaesthetic medicines and produces blood clotting factors. Elevated Alanine aminotransferase (ALT) – laboratory test, Aspartate aminotransferase (AST) – laboratory test or Total bilirubin – laboratory test results require investigation before surgery, rather than afterwards.

Viral screening: hepatitis B surface antigen, anti-HCV and HIV

These tests are standard in most hospitals and help protect both healthcare staff and patients (procedures may be modified if a result is positive). Anti-HBs testing (antibodies produced following hepatitis B vaccination) helps determine whether a patient is immune to hepatitis B. Many surgeons recommend vaccination before a planned procedure, which requires several weeks.

Urinalysis

Urinalysis helps detect asymptomatic urinary tract infections, which may be a contraindication to implant procedures (joint replacements and hernia meshes), as well as proteinuria and glycosuria.

Additional tests depending on the procedure and patient

• Orthopaedics (joint replacements, arthroscopy): additional C-reactive protein (CRP) and ESR testing (to exclude inflammation before implant insertion), often including 25-hydroxyvitamin D (25 OH) – vitamin D test and Total calcium – laboratory test.
• Ear, nose and throat surgery (tonsils, nasal septum): particular emphasis on coagulation tests and platelet counts because of the risk of bleeding; in children, a full blood count and clotting tests.
• Urology: urine culture (a negative result before endoscopic surgery), PSA testing in men and Creatinine – laboratory test.
• Bariatric and plastic surgery: Lipid profile (cholesterol) – laboratory test, Glycated haemoglobin (HbA1c), Thyroid-stimulating hormone (TSH) – laboratory test, albumin, Vitamin B12 – laboratory test, 25-hydroxyvitamin D (25 OH) – vitamin D test and Ferritin – laboratory test.
• Gynaecology: Beta human chorionic gonadotrophin (beta hCG) – pregnancy blood test for women of reproductive age on the day of surgery, and an up-to-date cervical screening test.
• Cardiology and patients over 50: ECG, possibly echocardiography and troponin; NT-proBNP in patients with heart failure.
• People with thyroid disorders: Thyroid-stimulating hormone (TSH) – laboratory test; uncontrolled hyperthyroidism or hypothyroidism is a contraindication to elective anaesthesia.
• Smokers and people with lung disease: chest X-ray and spirometry.

How long are preoperative test results valid?

There is no single regulation specifying validity periods; the hospital’s requirements apply. Typically, a full blood count, electrolytes, creatinine, glucose, coagulation tests and urinalysis are accepted for up to 14–30 days. Liver function and viral screening results are generally accepted for 1–3 months (up to 6 months in some centres). Confirmed blood group results remain valid indefinitely when documented on an identification card or established through two separate tests. ECG and chest X-ray results are usually accepted for 1–3 months. It is advisable to arrange testing 2–3 weeks before surgery: early enough to investigate any abnormalities, but late enough to ensure the results remain valid. Before your preoperative assessment, ask for a written list of required tests and their validity periods.

Common reasons for postponing surgery

• haemoglobin below 10 g/dl (many centres use thresholds below 12 g/dl in women and 13 g/dl in men for major surgery),
• potassium below 3.5 or above 5.5 mmol/l,
• INR above 1.5 in people not taking anticoagulants, or platelets below 100 000/µl,
• a positive urine culture or leukocyturia before implant surgery,
• glucose above 200 mg/dl or HbA1c above 8.5%,
• unexplained elevated CRP (possible infection involving, for example, a tooth or the sinuses),
• a respiratory tract infection within the previous 2 weeks.

Most of these problems can be investigated or treated within a few weeks, provided they are identified early. This is the strongest reason to arrange your tests well in advance rather than during the week of surgery.

Preparing for blood collection

Attend in the morning after fasting (12 hours), having avoided alcohol for 3 days and strenuous exercise the previous day. Anticoagulants and other regular medication should be taken according to your treating doctor’s instructions; do not stop taking them on your own before testing. An identity document is required for blood grouping and viral screening. For Urinalysis and urine culture, collect a first-morning, midstream urine sample in a sterile container.

Frequently asked questions

Do I have to undergo preoperative tests at the hospital?

Usually not. Hospitals generally accept results from external laboratories, provided they are within the required validity period. Some hospitals perform blood grouping in their own laboratories. It is worth confirming the requirements during your preoperative assessment.

Do I need a referral for preoperative blood tests?

No. You can purchase a ready-made test package tailored to your procedure online and have the tests performed at a blood collection centre. Hospitals accept results issued and authenticated by a laboratory.

How long does it take to receive the results?

Routine laboratory tests: 1 day. Viral screening and blood grouping: 1–3 working days. Urine culture: 2–4 days.

Sources

• NICE, Routine preoperative tests for elective surgery (NG45), 2016. nice.org.uk
• De Hert S. et al., European Society of Anaesthesiology, Eur J Anaesthesiol, Pre-operative evaluation of adults undergoing elective noncardiac surgery: updated guideline, 2018. doi.org
• Lamperti M. et al., ESAIC, Eur J Anaesthesiol, Preoperative assessment of adults undergoing elective noncardiac surgery, 2025. doi.org