4 mins read


Calcium is the most abundant mineral in the body, but fluctuations in blood levels can be a sign of illness or that your parathyroid glands are not working as they should be.

Author: Leanne Edermaniger

July 21, 2020

Reviewed by: Dr Thom Phillips

In this article:

What is Calcium?

Calcium makes up around 2% of your total body weight[1]. Calcium is important for building strong bones and teeth, muscle contraction[2], and normal blood clotting.

The human body cannot make calcium, so it must be acquired from the diet, making it an essential nutrient. Only 1% of the calcium in the body is found in the blood, the rest is present in teeth and bones[3].

How Much Calcium Do We Need?

Anyone aged over 19 needs 700mg of calcium each day[4]. Most people should be able to get all the calcium they need from their diet.

Osteoporosis is a condition that causes fragile bones. People receiving medication for osteoporosis may need to increase their daily calcium intake to 1000 mg[5].

What Causes High Calcium Levels?

Calcium levels are regulated by the parathyroid hormone and vitamin D. Parathyroid hormone is produced by the parathyroid glands. These are 4 small glands behind the thyroid gland in the neck. Parathyroid hormone is critical for calcium regulation in the body.

Parathyroid hormone levels rise when calcium levels drop, and decrease when calcium rises. Parathyroid hormone increases the absorption of calcium in the kidneys. It also facilitates the production of active vitamin D, which stimulates calcium absorption in the intestines for release into the blood. Together, parathyroid hormone and vitamin D keep calcium balanced[6].

If the calcium concentration in your blood is too high, it is called hypercalcaemia. Although calcium is essential for healthy bones and other functions, too much can be harmful, and in the most severe cases, life-threatening.

Several conditions can cause hypercalcaemia.


If one of the parathyroid glands becomes overactive, it causes an overproduction of parathyroid hormone, resulting in hyperparathyroidism. This causes a calcium imbalance and is the most common cause of hypercalcaemia[7].


  • Breast

  • Lung

  • Head and neck

  • Skin

  • Cervical

  • Kidney

  • Bladder

  • Oesophageal


Some medications and supplements are linked to high calcium levels, including diuretics, lithium, and calcium prescribed with antacids or vitamin D. Taking too much vitamin D or vitamin A can also cause hypercalcaemia.


Severe dehydration can cause hypercalcaemia, worsening dehydration and kidney function, resulting in severely high calcium levels[8].

Symptoms of High Calcium Levels

  • Being sick

  • Dehydration

  • Drowsiness

  • Confusion

  • Muscle spasms

  • Joint pain

  • Bone pain

  • High blood pressure

  • Irregular heartbeat[9]

How to Reduce Your Levels

If you are concerned your calcium levels are high, then there are things you can do to help bring them down. Speak to your GP to identify the underlying cause and any appropriate treatment.

  • Stay hydrated

    It’s important to keep topping up your fluid levels to avoid dehydration. Keep taking small sips throughout the day. A water bottle with a tracker to help you monitor your daily water intake could be useful if you need a physical reminder. You should avoid the feeling of thirst as this is an early sign of dehydration.

  • Lower your intake of calcium-rich foods

    Consider reducing your intake of calcium-rich foods such as milk, cheese, yoghurt, seeds (poppy, sesame, chia), whey protein, leafy greens, and salmon. These foods could be contributing to excess calcium levels.

  • Stop taking calcium supplements

    If you take low-dose calcium supplements or multivitamins that contain calcium, consider stopping to help bring your levels back within a normal range. If you take antacid tablets, check to see if they contain calcium, too.

What Causes Low Calcium Levels?

Low blood calcium levels are commonly caused by abnormal parathyroid hormone or vitamin D levels.


Hypoparathyroidism is a condition where the parathyroid glands do not produce enough parathyroid hormone, causing calcium levels to fall below normal and phosphorous levels to rise[10].

Vitamin D deficiency

Vitamin D is important in the regulation of calcium levels in the body. So, if deficiency occurs, this can cause a drop in calcium levels[11].

Kidney disease

The human body cannot make vitamin D, so we must expose our skin to sunlight and eat vitamin D-rich foods. When healthy, the kidneys convert this form of vitamin D into its active form which is used to help absorb calcium.

Chronic kidney disease means the kidneys are less able to convert vitamin D into its active form, consequently lowering calcium levels because the body can’t absorb calcium from food[12].

Other causes of hypocalcaemia are:

  • Medications

  • Genetic conditions

  • Low magnesium levels

  • Pancreatitis

Symptoms of Low Calcium Levels

  • Pins and needles

  • Muscle spasms or cramps

  • Muscle twitching

  • Seizures

How To Increase Your Levels

You can help support your calcium levels by eating calcium and vitamin D-rich foods.

Nutrient Food sources
Calcium Cheese (edam, gouda, cheddar, halloumi)
Tinned salmon
Green cabbage
Steamed broccoli
Vitamin D Oily fish
Red meat
Egg yolks
Fortified foods[13]


It’s also important to expose your skin to sunlight between March and October to keep your vitamin D levels within the optimum range. During this time you should be able to make all the vitamin D your body needs. However, during the autumn and winter months, the sun isn’t strong enough for vitamin D production, so it is recommended that all UK adults take a daily supplement containing 10mcg of vitamin D.

Most people will get all the calcium they need from their diet, but if you are going to take calcium supplements you mustn’t take too much. Taking more than 1500 mg of calcium a day can be harmful and cause side effects like stomach pain and diarrhoea.

Checking Your Calcium Levels

Calcium levels can be tested with a calcium blood test. The test requires a blood sample to be taken from a vein in your arm. If your calcium levels are abnormal, your GP may also request a urine sample, especially if it’s suspected you may have kidney stones.

A calcium test can be useful for anyone who suspects they may have:

  • Kidney stones

  • Kidney disease

  • Bone disease

  • Symptoms of high or low calcium levels

Calcium blood tests are also used to monitor people who have certain types of cancer.

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.

- Health scores calculated


Article references

  1. Fong, J., & Khan, A. (2012). Hypocalcemia: updates in diagnosis and management for primary care. Canadian family physician Medecin de famille canadien, 58(2), 158–162.

This article was written by Leanne Edermaniger

This information has been medically reviewed by Dr Thom Phillips

Thom works in NHS general practice and has a decade of experience working in both male and female elite sport. He has a background in exercise physiology and has published research into fatigue biomarkers.

Dr Thom Phillips

Dr Thom Phillips

Head of Clinical Services