How It Feels
The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
There is very little risk of
complications from having blood drawn from a vein.
- You may get a small bruise at the site. You
can lower the chance of bruising by keeping pressure on the site for several
- In rare cases, the vein may become swollen after the blood
sample is taken. This problem is called phlebitis. A warm compress can be used
several times a day to treat this.
- Ongoing bleeding can be a problem for people with bleeding
disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can
make bleeding more likely. If you have bleeding or clotting problems, or if you
take blood-thinning medicine, tell your doctor before your blood sample is
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Many conditions can change magnesium levels. Your
doctor will talk with you about any abnormal results that may be related to
your symptoms and past health.
What Affects the Test
High magnesium levels may be caused
Low magnesium levels may be caused
- Alcohol abuse or
- Complications from
diabetes, such as
- Diseases that block
with the way food is absorbed in the intestines, such as
- High blood calcium levels (hypercalcemia).
- Infection and swelling of
the pancreas (pancreatitis).
- Long-term diarrhea.
- Not getting enough
magnesium in the foods you eat.
- Pregnancy, especially in the second or third trimester.
parathyroid glands (hypoparathyroidism).