July 21, 2020

What is Calcium?

Calcium is one of the most abundant minerals in the human body. Approximately 99% of the calcium found in our body is stored in the bones, while the remaining 1% circulates in the blood.[1]

Calcium is essential for strong bones and teeth. However, it has other functions within the body such as helping our blood to clot, the heart to beat and muscles to contract.[2] Our bodies can’t produce their own calcium, so it must be acquired through the diet. Calcium is lost daily through sweat, urine, faeces as well as our hair skin and nails, so it’s important we replace what’s lost.

Why take a Calcium blood test?

A calcium blood test will measure how much calcium is in your blood. Having too much or too little calcium in your blood can indicate many conditions, including bone disease, thyroid disease or kidney disease.

The absorption of calcium by the body is dependent on vitamin D, without it the body is unable to produce the hormone needed for calcium absorption calcitriol. Without adequate amounts of calcium and vitamin D, bone health can be affected.

You can test your calcium levels by purchasing a simple at-home finger prick test kit which is then analysed at an accredited lab. Forth offers a number of blood tests which include calcium such as our best-selling Baseline Plus health check or our Nutri-check test.

What function does Calcium have in the body?

Calcium has many functions in the human body, all of which demonstrate how essential the mineral is. Many studies have shown that calcium has roles in:

  • Vascular contraction
  • Vasodilation
  • Nerve transmission
  • Intracellular signalling
  • Hormonal secretion
  • Muscle functions[3]

Calcium intake is particularly important during childhood and adolescence because it has a fundamental role in attaining peak bone mass. There are many studies which state the importance of weight-bearing exercise during childhood and adolescence for bone mass. While other studies state that prevention of osteoporosis should begin during childhood.[4] Equally, during adulthood, our calcium intake is important because it can influence on the level of age-related bone loss and an inadequate intake can cause osteoporosis. [5]

How do changes in Calcium affect health and wellbeing?

Being calcium deficient during key growth stages can have negative consequences for bone mass. Not consuming enough calcium in the diet alongside energy and protein intakes can cause the bones to have a low calcium content, which may be a risk factor for bone diseases or problems in later life.[6] There are some factors which influence bone mineral losses like physical activity, hormones and gender. For example, bone mineral is lost in females around the time of the menopause. Age and excessive loss of bone mineral density increase the risk of osteoporosis. Osteoporosis is a condition which causes weak bones making them fragile and increasing the risk of fracture. The symptoms of osteoporosis affect the quality of life and the condition is associated with increased mortality.[7]

Calcium can affect mental health. For example, hypercalcaemia (high calcium levels) has been associated with poor mental health.[8] However, there are other physical symptoms which can result in a poorer quality of life.

If you are worried about your calcium level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.

What can cause Calcium to change?

There are several conditions which can cause calcium levels to fluctuate. For example, hyperparathyroidism can cause an increase in blood calcium levels, although this is not always the case.[9] Hyperparathyroidism is a condition where the glands near the thyroid gland called the parathyroid glands produce too much parathyroid hormone.

Cancer can cause calcium levels to rise in the blood, however, this is usually in the advanced stages. Cancer can cause calcium to leak out into the bloodstream or can make it more difficult for the kidneys to get rid of it. Some cancers which may affect calcium levels are:

  • Myeloma
  • Breast
  • Lung
  • Kidney
  • Prostate

Dehydration from sickness and/or diarrhoea can also cause calcium levels to rise. High calcium levels need to be treated as they can make you very drowsy.[10]

Low calcium levels, on the other hand, are most commonly caused by low protein levels, particularly albumin. Other causes are:

  • Hypoparathyroidism
  • Alcoholism
  • Malnutrition
  • Reduced dietary intake of calcium
  • Low vitamin D levels
  • Bone disease


What are the most common symptoms?

The most common symptoms of hypercalcaemia are:

  • Bone pain
  • Fractures
  • Fatigue
  • Muscle weakness
  • Nausea
  • Vomiting
  • Stomach pain
  • Depression
  • Confusion[11]

A low level of calcium in the blood is also known as hypocalcaemia. Some people with hypocalcaemia won’t experience any symptoms, while others may have:

  • Pins and needles/numbness in the hands
  • Tingling around the mouth and lips
  • Muscle stiffness and weakness
  • Confusion
  • Breathing difficulties
  • Heart problems[12]

How to keep Calcium in the healthy range

We need both calcium and vitamin D for healthy, strong bones and teeth. The skin makes vitamin D after being exposed to the UVB rays of the sun. However, how much vitamin D the body makes and stores depends on the time of day, season, skin pigmentation, age and the country you are in. The three ways t get vitamin D are:

  • sunlight exposure
  • food
  • supplements

Age affects the skins ability to produce vitamin D and some people are at greater risk of low vitamin D such as individuals in care homes or who spend lots of time indoors. Alternatively, there are very few food sources which contain vitamin D such as:

  • oily fish
    • mackerel
    • salmon
    • tuna
  • fortified milk and dairy products
  • fortified cereals

If you are still unable to get enough vitamin D from sun exposure and diet, you may consider supplements.

Because the body must get its calcium from the diet, it is essential to eat the correct foods. The daily reference nutrient intake (RNI) for calcium is 700mg for males and females aged 19-50.[13] Good sources of dietary calcium are:

  • milk
  • cheese
  • yoghurt
  • soya beans
  • cabbage
  • broccoli
  • tofu
  • fortified bread

In terms of bone health, physical activity is an important factor. Exercise helps to keep bones healthy, strong and reduces the risk of falling. Some good physical activity examples are:

  • walking
  • weightlifting
  • resistance band training
  • gardening
  • using cross-training machines

Individuals who already have osteoporosis are encouraged to participate in regular exercise to help strengthen their bones and reduce the risk of fractures. It is advised to avoid high impact exercise.


[1] Lab Tests Online UK. (2018). Calcium Test.

[2] National Osteoporosis Association. (2019). Calcium/Vitamin D.

[3] Beto, J, A. (2015). The Role of Calcium in Human Aging. Clin Nutr Res: 4, pp 1-8.

[4] Lappe, J, M et al. (2014). The Longitudinal Effects of Physical Activity and Dietary Calcium on Bone Mass Accrual Across Stages of Pubertal Development. JBMR: 30(1), PP 156-164.

[5] Strӧhle, A., Hadji, P and Hahn, A. (2015). Calcium and Bone Health – Goodbye, Calcium Supplements? Climacteric: 18, pp 702-714.

[6] British Nutrition Foundation. (2005). Dietary Calcium and Health.

[7] NHS. (2019). Osteoporosis.

[8] Park, S and Hieber, R. (2016). Acute Psychosis Secondary to Suspected Hyperparathyroidism: A Case Report and Literature Review. Ment Health Clin: 6(6), pp 304-7.

[9] NHS. (2018). Hyperparathyroidism.

[10] Cancer Research UK. (2018). High Calcium in People with Cancer.

[11] Davidson, F. (2019). Hypercalcaemia.

[12] You and Your Hormones. (2018). Hypocalcaemia.

[13] British Nutrition Foundation. (2015). Nutrition Requirements.

View full list of biomarkers

This information has been medically reviewed by Dr Nicky Keay

Nicola has extensive clinical and research experience in the fields of endocrinology and sport and exercise medicine. Nicky is a member of the Royal College of Physicians, Honorary Fellow in the Department of Sport and Exercise Sciences at Durham University and former Research Fellow at St. Thomas' Hospital.

Dr Nicky Keay

Dr Nicky Keay

BA, MA (Cantab), MB, BChir, MRCP.