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Lab Tests Before Surgery: When you need them and when you don’t

If you’re going to have surgery, you may have blood and urine tests first. But most healthy people don’t need the tests, especially before low-risk surgery.

If you’re going to have surgery, you may have blood and urine tests first. These tests may be helpful if you have certain health conditions or diseases. For example, if you have a blood-clotting problem, a test can show if you’re at risk of too much bleeding during surgery.

But most healthy people don’t need the tests, especially before low-risk surgery. Here’s why:

The tests usually aren’t helpful for low-risk surgery.

Many healthy people have routine lab tests before surgery. In these cases, test results rarely change their surgeon’s decision to operate or make surgery safer.

The tests are especially unnecessary before low-risk surgery—such as eye, hernia, or skin surgery, or a breast biopsy. In these and many other surgeries, the risk of complications is very low.

The lab tests can lead to more tests.

Blood and urine tests are very safe, but they can cause false alarms. This can lead to anxiety and more tests. And it can needlessly delay your surgery. For example, one test may be followed up with a repeat test, an ultrasound, a biopsy, or a test that exposes you to radiation, such as an X-ray or CT scan.

When are the lab tests a good idea?

If you have certain health conditions or diseases, or your medical history shows the need, the tests may give your doctor helpful information. For example:

Based on the test results, your doctor may watch your condition more closely during or after your surgery. You may need to delay the surgery until a problem is under control. Or your doctor may change the procedures and anesthesia.


How should you prepare for surgery?

Your doctor or the hospital’s pre-surgery team will examine you and review your medical history.

These steps can help make your surgery safer:

Quit smoking, at least for the surgery. It is important not to smoke on the day of your surgery. The sooner you quit, the lower your risk of complications. If you need help quitting, ask your doctor.

Ask your doctor about your blood counts. If your red blood cell counts are low, ask your doctor about whether simple treatments like iron can be used to boost your red blood cells for surgery. That way, you can reduce the risk of needing a blood transfusion.

Ask about pain relief. Ask your doctor if you should stop aspirin or other blood thinners. You may want to use acetaminophen (Tylenol and generic) for pain relief. Avoid ibuprofen (Advil, Motrin IB, and generic) and naproxen sodium (Aleve and generic) because they can cause bleeding.

Ask for help. Ask someone to drive you to and from the hospital and stay overnight with you. You may want to ask someone to be with you at your doctor’s appointments, particularly in stressful situations, to be sure all instructions and information is retained. Ask about nursing or rehab care, too.

Pack a bag. Don’t bring valuables, but do bring: