Understand your Calcium Blood Test Results…

This page helps you to understand blood test results for Calciumand gives you the reference range to determine if your lab test results mean that you have high, low or normal Calcium levels. 

We outline the risk factors associated with both raised and lower Calcium levels.

Reference Ranges for Calcium:

Measurement unit Metric Optimal Risk
US Conventional Units mg/dl 8.8-10.4 <8.8 or > 10.4
Standard International Units mmol/L or mEq/L 2.2-2.6 <2.2 or > 2.6
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What is Calcium

Calcium, the most abundant mineral in the body, is found in some foods, added to others and is widely available as a dietary supplement. Levels of calcium in the blood are very tightly regulated and tend not fluctuate with changes in dietary intakes; the body uses bone tissue as a reservoir for, and source of calcium, to maintain constant concentrations of calcium in blood, muscle, and intercellular fluids [106].

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Function of Calcium

Calcium is required for heart function, muscle function, nerve transmission, intracellular signaling and hormonal secretion, though less than 1% of total body calcium is needed to support these critical metabolic functions. The remaining 99% of the body’s calcium supply is stored in the bones and teeth where it supports their structure and function [106].

Bone itself undergoes continuous remodeling, with constant resorption and deposition of calcium into new bone. The balance between bone resorption and deposition changes with age. Bone formation exceeds resorption in periods of growth in children and adolescents, whereas in early and middle adulthood both processes are relatively equal. In aging adults, particularly among postmenopausal women, bone breakdown exceeds formation, resulting in bone loss that increases the risk of osteoporosis over time [106].

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Risk factors associated with Calcium

Bone health and osteoporosis – When calcium intake is low or ingested calcium is poorly absorbed, bone breakdown occurs as the body uses its stored calcium to maintain normal biological functions. Bone loss also occurs as part of the normal aging process, particularly in postmenopausal women due to decreased amounts of estrogen. Many factors increase the risk of developing osteoporosis, including being female, thin, inactive, or of advanced age; smoking cigarettes; drinking excessive amounts of alcohol; and having a family history of osteoporosis [106].

Blood pressure and hypertension – Several clinical trials have demonstrated a relationship between increased calcium intakes and both lower blood pressure and risk of hypertension. In hypertensive subjects, calcium supplementation appears to lower systolic blood pressure, whereas calcium appears to have no significant effect on blood pressure where it is already in the normal range [106].

Preeclampsia – Preeclampsia is a serious medical condition in which a pregnant woman develops hypertension and proteinuria, usually after 20 weeks’ gestation. It is a leading cause of maternal and neonatal morbidity and mortality, affecting about 5–8% of pregnancies in the United States and up to 14% of pregnancies worldwide. Studies suggest that calcium supplementation during pregnancy reduces the risk of preeclampsia [106].

Weight management – Several studies have linked higher calcium intakes to lower body weight or less weight gain over time. Two explanations have been proposed. First, high calcium intakes might reduce calcium concentrations in fat cells by decreasing the production of parathyroid hormone and the active form of vitamin D. Decreased intracellular calcium concentrations in turn increase fat breakdown and discourage fat accumulation in these cells. Secondly, calcium from food or supplements might bind to small amounts of dietary fat in the digestive tract and prevent its absorption [106].

Health Risks from Excessive Calcium – Excessively high levels of calcium in the blood known as hypercalcemia can cause renal insufficiency, vascular and soft tissue calcification, hypercalciuria (high levels of calcium in the urine) and kidney stones [106].

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Notable variations by demographic group

Postmenopausal women – Menopause leads to bone loss because decreases in estrogen production increases bone resorption and decreases calcium absorption. Annual decreases in bone mass of 3%–5% per year frequently occur in the first years of menopause, and typically less than 1% per year after age 65 [106].

Individuals with lactose intolerance – Lactose intolerant individuals tend to be at higher risk of low calcium due to reduced dairy intake. Lactose intolerance refers to symptoms that occur when one consumes lactose, the naturally occurring sugar in milk [106].

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Diet to improve Calcium

Milk, yogurt, and cheese are rich natural sources of calcium and are the major food contributors of this nutrient. Non-dairy sources include vegetables, such as cabbage, kale, and broccoli. Spinach provides calcium, but its bioavailability is poor. Most grains do not have high amounts of calcium unless they are fortified [106].

Vitamin D is the most significant nutrient for the proper absorption of calcium. In addition to vitamin D, vitamin C, vitamin E, vitamin K, magnesium, and boron assist in absorbing calcium and also increasing bone mass.

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Supplements for Calcium

The two main forms of calcium in supplements are carbonate and citrate. Due to its dependence on stomach acid for absorption, calcium carbonate is absorbed most efficiently when taken with food, whereas calcium citrate is absorbed equally well when taken with or without food. Calcium citrate is also useful for people with achlorhydria, inflammatory bowel disease, or absorption disorders.

The percentage of calcium absorbed depends on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorption decreases. Absorption is highest in doses ≤500 mg. So, for example, one who takes 1,000 mg/day of calcium from supplements might split the dose and take 500 mg at two separate times during the day [106].

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Exercise to improve Calcium

Studies provide support for the idea that physical activity and dietary calcium intake together interact to produce a positive effect on bone mineral density [107]. Weight bearing exercise has received a lot of support in this area.

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Sleep for Calcium

Calcium is directly related to our cycles of sleep. In one study, published in the European Neurology Journal, researchers found that calcium levels in the body are higher during some of the deepest levels of sleep, such as the rapid eye movement (REM) phase. The study concluded that disturbances in sleep, especially the absence of REM deep sleep or disturbed REM sleep, are related to a calcium deficiency. Restoration to the normal course of sleep was achieved following the normalization of the blood calcium level [105].