ConditionHormones & metabolism
Calcium Deficiency
Calcium deficiency means your body is not getting or keeping enough calcium. It takes two forms. Long-term low dietary intake causes no symptoms at first, because the body takes calcium from bone, but over years it leads to thin bones (osteopenia and osteoporosis) and fractures. Low calcium in the blood (hypocalcemia) is different: it is usually caused by low vitamin D, parathyroid or kidney problems, and causes tingling, muscle cramps and spasms, and in severe cases seizures or heart rhythm problems.
Also called: Hypocalcemia, low calcium, calcium deficiency disease, dietary calcium deficiency
At a glance
- Two types
- Low calcium intake (affects bones over years) and low blood calcium, or hypocalcemia (affects nerves and muscles).
- Who is at risk
- Postmenopausal women, older adults, people avoiding dairy, those with low vitamin D or bowel conditions.
- Symptoms of low blood calcium
- Tingling around the mouth and fingers, muscle cramps and spasms, fatigue.
- Diagnosis
- Blood calcium, albumin, vitamin D, parathyroid hormone; bone density scan.
- Treatment
- Calcium-rich foods, vitamin D, supplements if needed, and treating the cause.
When to get help
Call 911 or go to the ER
- Seizures, severe muscle spasms, a tight throat or noisy breathing, or a very irregular heartbeat
- Muscle spasms or tingling after thyroid or parathyroid surgery that are getting worse quickly
See a doctor within a day or two
- Tingling around the mouth, fingers and toes with hand or foot cramps
- Known low calcium with confusion or palpitations
Book a routine appointment
- A fracture from a minor fall, or loss of height
- Diet with few dairy or calcium-fortified foods for years
- Long-term steroid use, an eating disorder, celiac disease, or early menopause
Usually safe to manage at home
- Occasional mild leg cramps at night without tingling or other symptoms
Why calcium matters
About 99% of the body's calcium is stored in bones and teeth. The remaining 1% in blood and cells is vital for muscle contraction, nerve signals, heart rhythm and blood clotting. The body keeps blood calcium in a narrow range using parathyroid hormone (PTH) and vitamin D. If intake is low, PTH pulls calcium out of bone to keep blood levels normal. That is why low intake does not show up in blood tests but quietly weakens bones.
How much calcium do you need
| Age group | Daily calcium (mg) |
|---|---|
| Children 1 to 3 | 700 |
| Children 4 to 8 | 1,000 |
| Ages 9 to 18 | 1,300 |
| Adults 19 to 50 | 1,000 |
| Men 51 to 70 | 1,000 |
| Women 51 and older | 1,200 |
| Everyone 71 and older | 1,200 |
| Pregnant or breastfeeding adults | 1,000 |
The safe upper limit for adults is 2,500 mg a day up to age 50 and 2,000 mg after 50, from food and supplements combined.
Symptoms
Long-term low intake
Usually no symptoms for years. Eventually:
- osteoporosis and bone fractures, especially wrist, hip and spine
- loss of height and stooped posture
- in children, poor bone growth and rickets (usually with vitamin D deficiency)
- possibly brittle nails and dental problems
Low blood calcium (hypocalcemia)
- tingling or numbness around the mouth, fingers and toes
- muscle cramps, twitching and spasms, especially in the hands and feet (carpopedal spasm), called tetany
- fatigue, irritability, anxiety and confusion
- dry skin and coarse hair (chronic)
- seizures, spasm of the voice box, heart rhythm problems and heart failure in severe cases
Causes
Low intake or absorption
- diets low in dairy and fortified foods, including some vegan diets
- lactose intolerance leading to dairy avoidance
- vitamin D deficiency, which reduces calcium absorption
- celiac disease, Crohn's disease and weight-loss surgery
- older age, when absorption falls
- high caffeine, salt and alcohol intake (small effects)
Low blood calcium
- vitamin D deficiency
- hypoparathyroidism, most often after thyroid or neck surgery
- chronic kidney disease
- low magnesium
- pancreatitis
- medicines: bisphosphonates, denosumab, some anti-seizure drugs, loop diuretics, proton pump inhibitors (long term)
- massive blood transfusion
Diagnosis
- Blood calcium, corrected for albumin, or ionized calcium
- Magnesium, phosphate and kidney function
- 25-hydroxy vitamin D
- Parathyroid hormone (PTH)
- Bone density (DEXA) scan for bone health, recommended for women 65 and older and younger people with risk factors
- ECG in hypocalcemia to look for a prolonged QT interval
Treatment
Getting enough from food
Good sources (approximate):
| Food | Calcium |
|---|---|
| 1 cup (240 ml) milk or fortified soy milk | About 300 mg |
| 6 oz (170 g) plain yogurt | About 300 mg |
| 1.5 oz (42 g) cheddar cheese | About 300 mg |
| 3 oz (85 g) canned sardines or salmon with bones | 180 to 325 mg |
| Calcium-set tofu, half cup | 250 to 400 mg |
| Fortified orange juice, 1 cup | About 300 mg |
| Cooked kale or bok choy, 1 cup | About 100 to 180 mg |
Spinach contains calcium but little of it is absorbed.
Supplements
- Use supplements only to fill the gap between food intake and needs.
- Calcium carbonate is cheapest and best taken with food. Calcium citrate can be taken anytime and is better absorbed in older people and those on acid reducers.
- Take no more than 500 mg at a time for best absorption.
- Supplements can cause constipation and bloating, and high doses raise the risk of kidney stones.
- Calcium can reduce absorption of thyroid hormone, some antibiotics and iron. Separate doses by several hours.
Vitamin D
Most adults need 600 to 800 IU of vitamin D a day. People with deficiency may need higher doses for a time, as advised by their doctor.
Treating hypocalcemia
Mild hypocalcemia is treated with oral calcium and vitamin D, and correcting low magnesium. Severe hypocalcemia is treated in hospital with IV calcium gluconate and heart monitoring. Hypoparathyroidism needs long-term calcium and active vitamin D (calcitriol), or parathyroid hormone replacement.
Frequently asked questions
What are the symptoms of calcium deficiency?
Low dietary calcium usually causes no symptoms until bones weaken and fracture. Low blood calcium causes tingling around the mouth and fingers, muscle cramps and spasms, tiredness and, when severe, seizures and heart rhythm problems.
What causes low calcium levels?
Low blood calcium is usually caused by vitamin D deficiency, low parathyroid hormone (often after neck surgery), kidney disease, low magnesium or certain medicines. Low intake mainly affects bones rather than blood levels.
How much calcium do adults need a day?
Most adults need 1,000 mg a day. Women over 50 and everyone over 70 need 1,200 mg. Teens need 1,300 mg. Try to get most of it from food and use supplements only to fill the gap.
Can too much calcium be harmful?
Yes. Getting more than 2,000 to 2,500 mg a day, mostly from supplements, can cause constipation and kidney stones, and very high blood calcium causes thirst, confusion and heart problems. Stick to recommended amounts.
Sources
This guide was written from current patient and clinical guidance, including:
- NIH Office of Dietary Supplements: Calcium fact sheet for health professionals
- National Academies (Institute of Medicine): Dietary Reference Intakes for Calcium and Vitamin D
- Bone Health and Osteoporosis Foundation: Calcium and vitamin D
- MedlinePlus: Hypocalcemia; Calcium in diet
- Endocrine Society: Hypoparathyroidism