Tests before a planned operation

In shortBefore planned surgery, hospitals usually ask for a complete blood count, a coagulation panel (INR, APTT, fibrinogen), glucose, creatinine, bilirubin, and ALT, plus infection screening and an ECG depending on age. Most results stay valid for 10–14 days, blood count and clotting often less. The practical move: confirm the exact list with the surgeon, then have blood drawn 5–7 days before the date.

What the standard set contains

The base of preoperative testing is a complete blood count: hemoglobin reveals anemia, white cells reveal inflammation, and platelets show the first line of clotting. Anemia raises surgical risk, so a low hemoglobin can move the operation date.

The second mandatory block is chemistry: glucose (uncontrolled diabetes impairs healing), creatinine (kidney function steers anesthesia dosing), bilirubin and ALT (liver status). Age and the type of surgery add an ECG, chest imaging, and infection markers.

Why clotting is checked before surgery

The surgeon needs to know how your blood will behave: INR and APTT time the two clotting pathways, and fibrinogen shows the reserve of clot material. Asymptomatic deviations are not rare, and learning about them before — not during — the operation is the entire point.

If you take anticoagulants or antiplatelet drugs (warfarin, apixaban, aspirin, clopidogrel), tell the surgeon early: only a doctor plans the pause or switch. Stopping these medications on your own is more dangerous than the surgery itself.

How long results stay valid

Preoperative results expire quickly: a blood count and clotting panel are usually good for 5–10 days, chemistry for 10–14, infection markers and ECG up to a month. Exact limits are set by the hospital and differ between institutions.

The working rule: consultation and a written list first, blood draw 5–7 days before the operation. Results stay fresh, and there is time to repeat a doubtful line without moving the date.

How to prepare for the draw

Blood is taken in the morning after 8–12 hours without food; plain water is allowed. Skip alcohol and hard training the day before — both shift ALT, glucose, and white cells. Smokers should avoid cigarettes for at least an hour beforehand.

Bring a list of everything you take: several common drugs affect clotting and chemistry, and the team reading your results needs that context. Photograph the reports immediately — paper forms have a way of disappearing before the operation date.

A typical preoperative minimum

Complete blood count with differential and platelets — valid 5–10 days
Coagulation panel: INR, APTT, fibrinogen — 5–10 days
Glucose, creatinine, bilirubin, ALT — 10–14 days
Infection screening per the hospital's list — up to a month
ECG depending on age and procedure — up to a month

Markers covered in this article

INR aPTT Fibrinogen D-dimer Hemoglobin White blood cells (WBC)Platelets (PLT)Creatinine Blood glucose Bilirubin ALT (alanine transaminase)

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Frequently asked questions

What happens if I arrive with expired results?

The operation will most likely be postponed: an anesthesiologist cannot work with outdated values. Count validity backward from the surgery date and confirm the requirements of your specific hospital.

Should I stop aspirin before surgery?

Only the doctor decides, weighing bleeding risk against clotting risk. Stopping antiplatelet or anticoagulant therapy on your own is dangerous — disclose every medication at the first consultation.

My white cells are slightly up — will the operation be cancelled?

It depends on the cause: an active infection is a reason to delay an elective procedure until recovery. A small shift without symptoms is judged individually, sometimes with a repeat draw.

Sources

Prothrombin time (PT): MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 31, 2026.
Partial thromboplastin time (PTT): MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 31, 2026.
Hemoglobin Test: MedlinePlus Medical Test — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.
Hemoglobin: MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.

Tests before a planned operation: the standard set and how long results stay valid