Calcium in Whole Blood or Urine

Clinical Information

Calcium is one of the seven major minerals and the most abundant in the body1. Calcium is well known for its structural role in the body. However, it is equally important for the excitability of muscles and nerves. It also activates fatty acid oxidation, a mitochondrial carrier for ATP and glucose stimulated release2.

Signs and Symptoms of Deficiency or Toxicity

Short-term Inadequate dietary intake of calcium do not normally lead to low calcium in the blood. Rather, it results from medical conditions such as renal failure, vitamin D deficiency, low blood magnesium levels, abnormal parathyroid function1,3.

Symptoms observed in hypocalcemia (low blood calcium) include numbness and tingling of fingers, muscle cramps, convulsions, lethargy, and poor appetite. Long-term hypocalcemia can result to osteopenia and if left untreated, cause osteoporosis3.

Adverse effects observed in people with high calcium levels in the blood include loss of appetite, nausea, vomiting, constipation, abdominal fatigue, and frequent urination3. It can also lead to renal insufficiency, vascular and soft tissue calcification, hypercalciuria, and kidney stones1.

Supplementation Guide

The World Health Organization (WHO) recommends calcium supplementation as part of antenatal care in populations where calcium intake is low. This is for the prevention of pre-eclampsia in pregnant women especially those at high risk of hypertension7. Following is the recommended dosage: 1.5-2.0 g elemental calcium/day to be given daily from 20 weeks gestation until the end of pregnancy. The total dosage must be divided into three doses and taken preferably during mealtimes. There is no established clinical guideline for calcium supplementation for the general adult population. However, in the event that calcium from the diet is not enough, calcium from supplements will be best absorbed by the body when taken in the amount of 500-600 mg, preferably with a meal8.

Following are the established upper limits for calcium per age group9.

  • For children, 1-18 y.o.: 2500 mg.
  • For adults, 19 to 70 y.o.: 3000 mg
  • For adults, 70 years and older: 2700 mg
  • For pregnant and lactating women: 2500 mg

Calcium supplements may interact with medications if taken together. It can cause decreased absorption of biphosphonates, fluoroquinolone and tetracyclines, levothyroxine, phenytoin, and tiludronate disodium1.

Food Sources

Milk and dairy products are excellent sources of calcium. It is also found in tofu, fortified beverages, fortified cereal, rhubarb, spinach, alons, white beans, bok choy, kale, pinto beans, red beans, and brocolli10.

(1) Office of Dietary Supplements-National Institutes of Health. (n.d.). Calcium. Fact Sheet for Health Professionals. Retrieved from
(2) Huskisson E, Maggini S, Ruf M. The role of vitamins and mineral in energy metabolism and well-being. The Journal of International Medical Research 2007; 35: 277-289
(3) Higdon J, Drake VJ, Delage B. (May 2017). Linus Pauling Isntitute. Micronutrient Center. Calcium. Retrieved from
(4) Mayo Clinic Medical Laboratories. (n.d.) Test Catalog. Calcium, Total, Serum. Retrieved from
(5) Gibson, R.M. (2005). Principles of Nutritional Assessment. New York: Oxford University Press, Inc.
(6) Kang SH, Cho KH, Park JW, Yoon KW, Do JY. Whole blood versus serum ionized calcium concentrations in dialysis patients. The Korean Journal of Internal Medicine. 2014;29(2):226-230. doi:10.3904/kjim.2014.29.2.226.
(7) WHO. Guideline: Calcium supplementation in pregnant women. Geneva, World Health Organization, 2013.
(8) National Osteoporosis Foundation. (n.d.). Calcium/Vitamin D. Retrieved from
(9) Philippine Dietary Reference Intakes. 2015. Department of Science Technology-Food and Nutrition Research Institute.
(10) Linus Pauling Institute. Oregon State University. (n.d.). Micronutrients for Health. Retrieved from