Blood test

Low calcium level in the blood

Blood test
Low calcium level in the blood
Last update: 05/03/2020

What is low calcium level in blood called?

  • Hypocalcaemia
  • Hypocalcemia

What is the normal level of calcium in the blood?

If you need to know which are the calcium reference ranges or you require more information about the role of calcium in the blood, you can visit normal calcium level in the blood

What does a low blood calcium level mean?

Calcium in the blood can be free, what is called ionized calcium, or can be bound to other substances (albumin, phosphorus, etc…). Only 40% of blood calcium is free or ionized.

In this document, we speak about total blood calcium. Sometimes, a blood test only measures free or ionized calcium, so the results are more or less 40% of the ranges showed above.

This document speaks about total blood calcium. If your blood test measures only free or ionized calcium, the ranges showed above will be different.

Blood albumin levels bound to calcium can alter the total blood calcium level. However, albumin level does not alter ionized calcium. Calcium biological functions depend mainly on ionized calcium rather than on total calcium.

Hypocalcemia or low blood calcium levels is usually present in case of suffering from hypoparathyroidism, malabsorption, pancreatitis or vitamin D deficiency.

Calcium blood values are usually given in mg/dl but sometimes you can see those values in mmol/l following the International System of Units (SI). In case your values are in mmol/l you can convert them using this tool:

  • Mild hypocalcemia (8 - 8.5 mg/dL in adults):

    Calcium blood level is a bit low but it is not usually a cause for concern.

    You must watch your diet. You should increase your calcium and D vitamin intake. For this purpose, it is adequate to take dairy products.

    If you follow this recommendation your calcium level will be optimal in your following test.

  • Moderate hypocalcemia (7 - 8 mg/dL in adults):

    Moderate Hypocalcemia requires follow up.

    Patients often complain of cramping, numbness or tingling in their fingertips, and paresthesia of the extremities.

    It is recommended a visit to your doctor because moderate hypocalcemia can be caused by an underlying disease.

  • Marked hypocalcemia (6.4 - 7 mg/dL in adults):

    Marked hypocalcemia is a matter of concern. Seizures can be induced by hypocalcemia.

    You may require hospitalization because calcium should be administered intravenously in order to increase calcium blood level.

  • Severe hypocalcemia (< 6.4 mg/dL in adults):

    You need to look for urgent medical attention. It is common in severe hypocalcemia to have seizures or tetany. Tetany is a serious complication characterized by involuntary contraction of muscles.

    You can also suffer from arrhythmias and a heart attack is a possibility.

Which factors can reduce calcium blood levels?

  • Magnesium deficiency
  • Vitamin D deficiency
  • Malabsorption
  • Massive transfusion
  • Drugs
    • Antibiotics
      • Rifampicin
    • Antiepileptic drugs
      • Phenytoin
      • Phenobarbital
    • Antirheumatic drugs
      • Chloroquine
    • Bisphosphonates
      • Zoledronate
      • Alendronate
      • Ibandronate
      • Risedronate
    • Corticosteroids

Which diseases can reduce your calcium blood levels?

The following diseases can explain a calcium blood level lower than normal:

  • Rickets
  • Alkalosis
  • DiGeorge syndrome

What can I do to increase calcium blood levels?

If your calcium blood level is low, the following tips can help you:

  • Increase your calcium intake. The main foods rich in calcium are:
    • Dairy products: milk, yogurt, cheese
    • Vegetables: Leafy greens like spinach, kale, broccoli, turnip
    • Fish: sardines, salmon
  • You can also take calcium supplements (for example calcium carbonate or fortified cereals). D vitamin increases calcium absorption.

Where can I find more information about calcium in the blood?

You can visit our pages about:

Which values are considered a low calcium level in the blood?

The following values are considered to be below the normal range:

IMPORTANT: These levels are expressed in mg/dl. They are an example of a healthy man of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

Mild hypocalcemia
8.4 mg/dL8.3 mg/dL8.2 mg/dL8.1 mg/dL8 mg/dL   
Moderate hypocalcemia
7.9 mg/dL7.8 mg/dL7.7 mg/dL7.6 mg/dL7.5 mg/dL7.4 mg/dL7.3 mg/dL7.2 mg/dL
7.1 mg/dL7 mg/dL      
Marked hypocalcemia
6.9 mg/dL6.8 mg/dL6.7 mg/dL6.6 mg/dL6.5 mg/dL6.4 mg/dL  
Severe hypocalcemia
6.3 mg/dL6.2 mg/dL6.1 mg/dL6 mg/dL5.9 mg/dL5.8 mg/dL5.7 mg/dL5.6 mg/dL
5.5 mg/dL5.4 mg/dL5.3 mg/dL5.2 mg/dL5.1 mg/dL5 mg/dL4.9 mg/dL4.8 mg/dL
4.7 mg/dL4.6 mg/dL4.5 mg/dL4.4 mg/dL4.3 mg/dL4.2 mg/dL4.1 mg/dL4 mg/dL
3.9 mg/dL3.8 mg/dL3.7 mg/dL3.6 mg/dL3.5 mg/dL3.4 mg/dL3.3 mg/dL3.2 mg/dL
3.1 mg/dL3 mg/dL2.9 mg/dL2.8 mg/dL2.7 mg/dL2.6 mg/dL2.5 mg/dL2.4 mg/dL
2.3 mg/dL2.2 mg/dL2.1 mg/dL2 mg/dL1.9 mg/dL1.8 mg/dL1.7 mg/dL1.6 mg/dL
1.5 mg/dL1.4 mg/dL1.3 mg/dL1.2 mg/dL1.1 mg/dL1 mg/dL  
Medically reviewed by Javier Muga Bustamante Ph.D. on 05/03/2020


  • Concise Book of Medical Laboratory Technology: Methods and Interpretations. 2nd Edition. 2015. Ramnik Sood. ISBN: 978-93-5152-333-8. Pag. 493.
  • Thomas L, ed. Clinical Laboratory Diagnostics Use and Assessment of Clinical Laboratory Results, 1st ed. Frankfurt/Main: TH-Books Verlagsgesellschaft, 1998:231-241.
  • Common Terminology Criteria for Adverse Events (CTCAE). Version 5.0.Published: November 27, 2017. U.S. Department of health and human Services. Available on:
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