A health care professional will take a blood sample from a vein or an artery. Blood from an artery may provide more accurate results than blood from a vein, so your provider may recommend this type of blood test, which is called an arterial blood gas (ABG) test.
To take a blood sample from a vein, a health care professional will insert a small needle into your arm. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes. Make sure you don't clench your fist during the test, as this can temporarily raise lactate levels.
To take a blood sample from an artery, a provider will usually use an artery inside the wrist. But the sample may be taken from an artery in your arm or groin. For a newborn, the sample may be taken from the baby's heel or the umbilical cord shortly after birth.
If your blood sample is taken from your wrist, the provider will first test your blood circulation. The provider will hold your wrist and apply pressure to the arteries to cut off blood flow to your hand for several seconds. Then the provider will let go of your wrist to check how quickly blood flow returns to your hand. If your blood flow is normal, the provider will collect a blood sample.
A blood sample taken from an artery tends to be more uncomfortable than most blood tests, which use a vein. So, the provider may apply some numbing medicine to your skin first. The provider will insert a needle with a syringe into the artery to remove some blood.
When the syringe is full, the provider will bandage the puncture site. Pressure will be applied to the site for at least 5 minutes to stop the bleeding.
If meningitis is suspected, your provider may also take a sample of your cerebrospinal fluid in a procedure called a spinal tap or lumbar puncture. This is usually done in a hospital.