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Blood tests in hospital

If you stay in a hospital overnight or longer, you may have many blood tests. Sometimes you need all the tests, especially if you are very sick. But sometimes you get more tests than you need. Here’s what you should know about blood tests in the hospital.

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Common blood tests

When you’re in the hospital, you may have blood taken for 2 common tests.

  • A full blood count (FBC) checks your blood for signs of infection, immune system problems, bleeding problems, and anaemia (low iron).
  • A blood chemistry panel gives your doctor information about your muscles, bones, heart, and other organs. It also checks your blood sugar, calcium, and other minerals.

These tests can help your doctor identify a problem and learn if a treatment is working.

More testing doesn’t help you

If your test results stay the same after a day or two, you may not need them again. More tests won’t tell your doctor anything new, unless you’re in intensive care or your treatment changes.

Less testing doesn’t hurt you

There’s no harm in having fewer tests. One study showed that reducing common tests at the hospital did not affect patient health or safety.

The risks

Blood tests are very safe. But they can cause other problems if you have them every day.

  • Anaemia. This can happen if you lose too much blood. With anaemia, your blood cells can’t carry enough oxygen to the rest of your body. Anaemia can make it harder for you to heal. It is especially dangerous for people with heart or lung problems.
  • Increased risk of infection. Blood tests have a low risk of infection. But the more tests you have, the more risk you have.
  • Less sleep. Nurses often wake patients up to get blood tests. Poor sleep can affect how you heal.

You may need a blood test every day if:

  • You are in intensive care.
  • The doctors don’t know what’s wrong with you.
  • You are trying a new treatment.
  • Your doctor thinks you may have internal bleeding, especially if you’re having surgery.

Other tests you may not need

If you’re scheduled to have surgery, your doctor may want you to have certain tests. These are usually done before the day of your surgery. Consider the tests below only if you have certain problems or need some kinds of surgery:

  • Blood coagulation test. May be needed if you’re having brain, cancer, heart, or spinal surgery. You may also need it if you have certain medical conditions or take blood thinners.
  • Breathing test. Recommended if you’re having lung, chest, or upper abdominal surgery. You may also need it if you have lung disease or are short of breath.
  • Cardiac stress test. May be needed if you have heart disease, especially if you are having major surgery.
  • Chest X-ray. May be needed if you smoke, have symptoms of lung or heart disease, or are older than 70, especially if you’re having major surgery.

This report is for you to use when talking with your health professional.

It’s OK to ask questions
If you have questions about your symptoms or the medicines managing your symptoms, speak with your health professional.

You can also download this information as a pdf (462 KB).

© 2015 Consumers Union of United States, Inc, (101 Truman Ave, Yonkers, NY 10703-1057). Adapted from Consumer Reports (2015), Blood tests when you’re in the hospital, developed in co-operation with the Society of Hospital Medicine. Choosing Wisely does not assume any responsibility or liability arising from any error or omission or from the use of any information in these resources.

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Choosing Wisely

This article is part of our content on Choosing Wisely, a campaign encouraging a change in thinking by health professionals and consumers to avoid unnecessary medical intervention.

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