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Purpose of serum calcium (Indications)

  1. Serum level of calcium is used to evaluate parathyroid function and metabolism.
  2. Serum calcium level is used to monitor renal failure and renal transplantation.
  3. Serum calcium level is used to evaluate hyperparathyroidism.
  4. Serum calcium level may be done in malignancies like multiple myeloma.
  5. Serum calcium level may be done to monitor calcium level before and after blood transfusions.

Pathophysiology of Calcium

  1. There is a large amount of calcium in the body and mainly in the bones and teeth.

  1. Normally the level of calcium in the blood is carefully controlled. When blood calcium levels get low Hypocalcemia, the bones release calcium to bring it back to a good blood level.
  2. When blood calcium levels get high Hypercalcemia, the extra calcium is stored in the bones or passed out of the body in stool and urine.
  3. The calcium is also needed to maintain metabolic process like as muscle contraction, transmission of neural impulses, clotting of the blood, cardiac function and inhibit cell destruction,
  4. Daily intake of about 400 mg is needed by the body.
  5. Body serum calcium levels are maintained by a balance between parathyroid Hormone PTH (Parathyroid gland hormone) and calcitonin (produced by C or parafollicular cells of thyroid).

  1. PTH increases the serum calcium level by increasing bone resorption and mobilizing Calcium.
  2. PTH indirectly increases the absorption of calcium from the gastrointestinal tract by the production of the vit. D.

                                                                                           Calcium metabolism and control

  1. PTH also increases the excretion of phosphate in the urine.
  2. Calcitonin decreases serum calcium and phosphate levels by inhibiting bone resorption.
  3. Decrease calcium level increases PTH which acts on the reservoir of calcium and lead to its release in the circulation.
  4. Half of the calcium in blood circulation is free in ionized form and half is in the protein-bound form mostly with albumin.
    1. 50% free or ionized (active) form.
    2. 40% is bound to protein.
    3. 10% is complexed with anions.


  1. In a patient with low serum albumin will have low serum calcium.
    1. So serum albumin level may be estimated with serum calcium level. Serum calcium level decreases 0.8 mg with every decrease of 1 gram albumin.
  2. Some physician prefers ionized serum calcium level to avoid the effect of albumin level.
  3. To label hypercalcemia, one should have three separate raised level of calcium.

  1. Symptoms of hypercalcemia are:
    1. anorexia.
    2. Nausea.
    3. Vomiting.
    4. Ultimately coma.
  2. The ectopic PTH-like hormone may be secreted by the tumors of lung, breast, and kidney.
  3. Symptoms of hypocalcemia shows:
    1. Nervousness.
    2. Excitability.
    3. Tetany.

A normal level of total serum Calcium

Source 1

Source 2

Age  mg/dL
Cord blood 8.2 to 11.2
Premature 6.2 to 11.0
0 to 10 days 7.6 to 10.4
10 days to 2 years 9.0 to 11.0
2 years to 12 years  8.8  to 10.8
12  to 18 years 8.4 to 10.2
18 to 60 years 8.6 to 10 .0
60 to 90 years 8.8 to 10.2
>90 years 8.2 to 9.6

Hypercalcemia may be seen in the following conditions (plasma level >10.5 mg/dL):

  1. Hyperparathyroidism.
  2. Hyperthyroidism.
  3. Metastatic bone tumor of lung, breast, and kidney.
  4. Milk-alkali syndrome.
  5. Multiple myelomas.
  6. Paget’s disease.
  7. Sarcoidosis.
  8. Tumors producing a PTH-like substance.
  9. Vitamin D intoxication.
  10. Excessive calcium intake.
  11. Prolonged immobilization.
  12. Thiazide diuretics.
  13. Withdrawal of steroids.
  14. The majority (80 to 90 %) of the hypercalcemia cases are due to hyperparathyroidism or malignancy.

Hypocalcemia may be seen in the following conditions (plasma level <8.5 mg/dL):

  1. Hypoparathyroidism.
  2. Pseudohypoparathyroidism due to lack of response to PTH. 
  3. Malabsorption (inadequate absorption of nutrients from the intestinal tract).
  4. Hypoalbuminemia.
  5. Osteomalacia
  6. Pancreatitis
  7. Renal failure (chronic).
  8. Rickets and vitamin D deficiency
  9. Liver disease (decreased albumin production).
  10. Hypomagnesemia.
Tabulated differential diagnosis of Hypercalcemia (Raised Calcium)
Clinical condition           
 Etiological  causes
Primary hyperparathyroidism        Parathyroid adenoma
Parathyroid carcinoma
Tertiary hyperparathyroidism due to post- renal transplant
Drugs  Thiazides
An antacid containing calcium
Milk-alkali syndrome
Granulomatous diseases Sarcoidosis

Endocrine abnormality Hyperthyroidism
Addison's disease
cancers In most of the malignant tumors
Multiple myelomas
Renal cell carcinoma
Liver cell carcinoma
Islet cell tumor
Ovary Carcinoma

 Natural foods good source of calcium: 

Food  Quantity Amount of calcium
Kale  one cup 245 mg
Milk   one cup  305 mg 
Yogurt 6 oz  300 mg
Cheese one oz 224 mg
Dried figs 8 whole figs 107 mg
 White Beans one cup  191 mg 
Turnip greens one cup  195 mg
Black-eyed beans 1/2 cup  185 mg
Canned salmon 1/2 cup  232 mg
Orange juice  one cup  500 mg
Orange one medium  65 mg
Sesame seed one teaspoon  88 mg
Almond 1/2 cup dry roasted 72 mg
Instant oatmeal one cup 187 mg
Soy milk one cup  300 mg
Firm Tofu 1/2 cup  861 mg
Broccoli one cup 


62 mg

Critical values:


Possible References Used

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