Calcium Blood Test
What is a calcium blood test?
A calcium blood test measures the level of calcium in your blood.
There are two types of calcium blood tests:
- Total calcium: This test measures the calcium attached to certain proteins in your blood and “free” or unattached calcium. Total calcium is often included in a routine blood screening test called a basic metabolic panel (BMP).
- Ionized calcium: This test measures the calcium that is unattached or "free" from certain proteins in your blood.
A calcium blood test cannot show how much calcium you have in your bones. Your healthcare provider can measure your bone health with a type of X-ray called a bone density test (DEXA scan).
What is calcium and what does it do?
Calcium is one of the most important and common minerals in your body. About 99% of your body’s calcium is stored in your bones and teeth, while the other 1% of it circulates in your blood. Although it may be a small amount, the calcium in your blood is essential and does the following:
- Helps your nerves work.
- Helps make your muscles squeeze together so you can move.
- Helps your blood clot if you are bleeding.
- Helps your heart work properly.
The levels of calcium in your blood and bones are controlled by two hormones called parathyroid hormone (PTH) and calcitonin. Vitamin D also plays an important role in maintaining calcium levels because your body needs it in order to absorb calcium.
Why do I need a calcium blood test?
There are four main reasons why you may need a calcium blood test, including:
- Your healthcare provider may have ordered routine bloodwork called a basic metabolic panel (BMP) or comprehensive metabolic panel (CMP), which both include a calcium blood test.
- You may be showing signs or symptoms of having too much calcium (hypercalcemia) or too little calcium (hypocalcemia) in your blood.
- If you’ve been diagnosed with a condition that affects the amount of calcium in your blood, you may need routine calcium blood tests to make sure your treatment is working.
- If you take a medication that affects the amount of calcium in your blood, you may need routine calcium blood tests to monitor your levels.
Signs and symptoms of having too much calcium in your blood (hypercalcemia) include:
- More frequent urination and increased thirst.
- Nausea and vomiting.
- Loss of appetite.
- Constipation and abdominal pain.
Signs and symptoms of having too little calcium in your blood (hypocalcemia) include:
- Muscle cramps, especially in your back and legs.
- Dry, scaly skin.
- Brittle nails.
- Irritability or restlessness.
Severe hypocalcemia (very low levels of calcium in your blood) can cause the following symptoms:
- Tingling in your lips, tongue, fingers and/or feet.
- Muscle aches.
- Muscle spasms in your throat that make it difficult to breathe.
- Stiffening and spasms of your muscles (tetany).
- Abnormal heart rhythms (arrhythmia).
Your healthcare provider may order a calcium test if you have a medical condition that may affect your calcium levels. Many medical conditions affect your blood calcium levels, including:
- Parathyroid conditions.
- Kidney disease.
- Thyroid disease.
- Malnutrition, especially too little or too much calcium and/or vitamin D in your diet.
- Certain types of cancer.
Certain medications can also affect your blood calcium levels, including:
- Hydrochlorothiazide (HCTZ) and other thiazide diuretics.
- Excess intake of calcium carbonate in the form of Tums® or Rolaids®.
Who performs a calcium blood test?
A healthcare provider known as a phlebotomist usually performs blood draws, but any healthcare provider who is trained in drawing blood can perform this task. The samples are sent to a lab where a medical laboratory scientist prepares the samples and performs the test on machines known as analyzers.
How do I prepare for a calcium blood test?
You don’t need to follow any special instructions before a calcium blood test if it’s your only test.
Your calcium blood test may be part of a basic or comprehensive metabolic panel, which measures multiple things in your blood. In this case, you may need to not eat or drink (fast) for several hours before your blood draw. In any case, your healthcare provider will let you know if you need to follow any special instructions.
What should I expect during my calcium blood test?
You can expect to experience the following during a blood test, or blood draw:
- You’ll sit in a chair, and a healthcare provider will check your arms for an easily accessible vein. This is usually in the inner part of your arm on the other side of your elbow.
- Once they’ve located a vein, they’ll clean and disinfect the area.
- They’ll then insert a small needle into your vein to take a blood sample. This may feel like a small pinch.
- After they insert the needle, a small amount of blood will collect in a test tube.
- Once they have enough blood to test, they’ll remove the needle and hold a cotton ball or gauze on the site to stop the bleeding.
- They’ll place a bandage over the site, and you’ll be finished.
The entire procedure usually takes less than five minutes.
What should I expect after my calcium blood test?
After a healthcare provider has collected your blood sample, they’ll send it to a laboratory for testing. Once the test results are back, your healthcare provider will share the results with you.
What are the risks of a calcium blood test?
Blood tests are a very common and essential part of medical testing and screening. There’s very little risk to having blood tests. You may have slight tenderness or a bruise at the site of the blood draw, but this usually resolves quickly.
Results and Follow-Up
What do the results of a calcium blood test mean?
Blood test reports, including calcium blood test reports, usually provide the following information:
- The name of the blood test or what was measured in your blood.
- The number or measurement of your blood test result.
- The normal measurement range for that test.
- Information that indicates if your result is normal or abnormal or high or low.
What are normal blood calcium levels?
In most cases, a normal blood calcium level for adults is 8.5 to 10.2 milligrams/deciliter (2.15 to 2.55 millimoles/liter). However, laboratories may have different reference ranges for normal blood calcium levels. You shouldn’t compare values from one laboratory to normal ranges from another laboratory.
When you get your blood test results back, there will be information that indicates what that lab’s normal blood calcium range is. If you have any questions about your results, be sure to ask your healthcare provider.
What does a high calcium blood level mean?
If your results reveal that you have higher-than-normal levels of calcium in your blood, it may indicate that you have:
- Lung diseases such as sarcoidosis and tuberculosis.
- Kidney failure.
- Lung cancer.
- Breast cancer.
- Certain cancers of the blood.
- Hyperthyroidism (an overactive thyroid).
- Paget’s disease of the bone.
- Multiple myeloma.
It’s important to remember that a high calcium result doesn’t necessarily mean that you have a medical condition. Certain medications can also increase your blood calcium levels.
What does a low calcium blood level mean?
If your results reveal that you have lower-than-normal levels of calcium in your blood, it may indicate that you have:
- Vitamin D deficiency.
- Kidney failure (renal failure).
- Celiac disease or other conditions that cause malabsorption.
It’s important to remember that a low calcium result doesn’t necessarily mean that you have a medical condition. Certain medications and diets can also decrease your blood calcium levels.
Should I be concerned if I have high or low blood calcium results?
If your calcium blood test results reveal that you have high or low levels of calcium, it doesn't necessarily mean that you have a medical condition. Other factors, such as diet and certain medications, can affect your calcium levels. There could’ve also been an error in the collection, transport or processing of the test.
If you have an abnormal result, your healthcare provider may order additional tests to determine the cause of your abnormal calcium levels. The additional tests may measure your:
- Ionized blood calcium.
- Urine calcium.
- Vitamin D.
- Parathyroid hormone (PTH).
- Thyroid hormones.
If you have questions about your results, don’t be afraid to talk to your healthcare provider.
When should I know the results of my calcium blood test?
In most cases, you should have your blood calcium test results within one or two days, though it could take longer.
When should I call my doctor?
If you’re experiencing concerning symptoms of hypocalcemia or hypercalcemia, contact your healthcare provider as soon as possible.
A note from Cleveland Clinic
Seeing an abnormal test result can be stressful. Know that having a high or low level of blood calcium doesn’t necessarily mean you have a medical condition and need treatment. Approximately 1 in 20 healthy people will have results outside of the normal range. Your healthcare provider will let you know if you need to undergo further tests to determine the cause of the abnormal level. Don’t be afraid to ask your provider questions. They’re there to help you.
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