If you stay in a hospital overnight or longer, you may have many blood tests. Sometimes you need all these 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.

Common blood tests.

When you’re in the hospital, you may have blood drawn for two common sets of tests.

  • A complete blood count (CBC) checks your blood for signs of infection, immune system problems, bleeding problems, and anemia (low iron).
  • A blood chemistry panel gives your health care provider information about your muscles, bones, heart, and other organs. It may also include checks for your blood sugar, liver, calcium, and other minerals.

These tests can help your health care provider identify a problem and learn if a treatment is working.

More testing doesn’t always help you.

If your test results stay the same after a day or two, you may not need them again. In some cases, more tests won’t tell your health care provider 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. Several studies show that reducing common tests at the hospital did not affect patient health or safety.

Getting too many blood tests has risks.

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

  • Anemia. This can happen if you lose too much blood. With anemia, your blood cells can’t carry enough oxygen to the rest of your body. Anemia can make it harder for you to heal. It is especially dangerous for people with heart or lung problems. You may be more likely to get anemia if you are unable to eat normally due to your illness.
  • Increased risk of infection. Needle pokes for blood tests have a low risk of infection. But the more tests you have, the more risk you have.
  • Bleeding and bruising. The more needle pokes you have, the higher the chances of getting bruising or bleeding from a poke site. This risk is higher if you are taking blood thinners.
  • Less sleep. You may be woken up to get blood tests. Poor sleep can affect how you heal.

You may need a blood test every day if:

  • You are seriously ill or in intensive care.
  • Your health care team wants to better understand your symptoms.
  • You are trying a new treatment.
  • Your health care provider thinks you may have internal bleeding or a new infection, especially if you’ve had surgery.

Ask your health care provider why you have blood tests every day.

It’s okay to ask your health care provider why you need more blood tests. Ask if the test gives new information or is likely to help your treatment.