Calcium
Builds bones and teeth; needed for muscle contraction, nerve signals and blood clotting.
If you are short of it
Possible signs
- Muscle cramps or twitching
- Bone or joint pain
- Tingling or numbness in hands and feet
- Fragile bones, easy fractures
- Brittle or ridged nails
- Palpitations (fast heartbeat)
These signs are common and have many other causes. They are clues, not proof; a blood test and a doctor can tell.
Who is more at risk
Dairy-free diets, lactose intolerance, post-menopausal women, teenagers, older adults, long-term steroid use, coeliac disease.
Foods rich in Calcium
| Food | Serving | Amount | women 19–50 | men 19–50 |
|---|---|---|---|---|
| Plain yogurt (low-fat) | 1 cup (245 g) | 415 NIH | 42% | 42% |
| Sardines (canned, with bones) | 1 can (90 g drained) | 350 NIH | 35% | 35% |
| Milk (fortified) | 1 cup (240 ml) | 300 NIH | 30% | 30% |
| Cheese (cheddar type) | 40 g, about 2 slices | 285 NIH | 28% | 28% |
| Tofu (firm, calcium-set) | ½ cup (125 g) | 250 NIH | 25% | 25% |
| Molokhia (cooked) | 1 cup (90 g leaves) | 184 | 18% | 18% |
| Tahini (sesame paste) | 2 tablespoons | 128 | 13% | 13% |
| Spinach (cooked) | ½ cup (90 g) | 123 NIH | 12% | 12% |
| Dried figs | 4 figs (60 g) | 97 | 9.7% | 9.7% |
| Corn tortillas | 2 tortillas | 92 NIH | 9.2% | 9.2% |
| Chickpeas | 1 cup cooked | 80 | 8% | 8% |
| Bok choy (cooked) | ½ cup (85 g) | 79 NIH | 7.9% | 7.9% |
| Almonds | a small handful (28 g) | 76 | 7.6% | 7.6% |
| Okra (cooked) | ½ cup (80 g) | 62 | 6.2% | 6.2% |
Unit: mg. Share of the daily amount. Values marked NIH were checked against the food tables of the NIH Office of Dietary Supplements; the others are approximate and unchecked. Real foods vary with variety, brand, soil and cooking.
As a supplement
Calcium carbonate (take with food) or calcium citrate (any time; better with acid reducers). Take no more than about 500 mg at once; split larger totals.
Too much
Too much from supplements: constipation, kidney stones, high blood calcium; some studies link high-dose supplements to heart risk, so food first.
How much you need each day
| Group | Recommended | Upper limit |
|---|---|---|
| Infants 0–6 months | 200 | 1000 |
| Infants 7–12 months | 260 | 1500 |
| Children 1–3 years | 700 | 2500 |
| Children 4–8 years | 1000 | 2500 |
| Children 9–13 years | 1300 | 3000 |
| Boys 14–18 years | 1300 | 3000 |
| Girls 14–18 years | 1300 | 3000 |
| Men 19–30 years | 1000 | 2500 |
| Women 19–30 years | 1000 | 2500 |
| Men 31–50 years | 1000 | 2500 |
| Women 31–50 years | 1000 | 2500 |
| Men 51–70 years | 1000 | 2000 |
| Women 51–70 years | 1200 | 2000 |
| Men over 70 | 1200 | 2000 |
| Women over 70 | 1200 | 2000 |
| Pregnant 14–18 years | 1300 | 3000 |
| Pregnant 19–30 years | 1000 | 2500 |
| Pregnant 31–50 years | 1000 | 2500 |
| Breastfeeding 14–18 years | 1300 | 3000 |
| Breastfeeding 19–30 years | 1000 | 2500 |
| Breastfeeding 31–50 years | 1000 | 2500 |
Unit: mg. Includes calcium from food and supplements. US/Canada Dietary Reference Intakes (National Academies), as summarised by the NIH Office of Dietary Supplements. Other countries’ values differ slightly. These are amounts for healthy people, not treatment doses.
Interactions
Avoid together · Iron
Calcium reduces iron absorption. Take iron and calcium (also dairy, tea, coffee) at least 2 hours apart.
Take care · Zinc
Large calcium doses can slightly reduce zinc absorption.
Take care · Magnesium
High doses of calcium and magnesium compete for absorption. Split them: for example calcium with lunch and magnesium in the evening.
Works together · Vitamin D
Vitamin D increases calcium absorption. Low vitamin D makes calcium supplements work poorly.
Take care · Vitamin D
Very high calcium together with very high vitamin D can raise blood calcium. Stay within the upper limits.
Medicines and habits to mention to your doctor
Levothyroxine (thyroid hormone)
Take it alone on an empty stomach and wait about 4 hours before calcium, iron or magnesium supplements.
Tetracycline, doxycycline, ciprofloxacin, levofloxacin
Minerals bind these antibiotics. Usually take the antibiotic 2 hours before or 4–6 hours after the supplement or dairy; check the leaflet.
Acid reducers (omeprazole, esomeprazole, famotidine)
Long-term use lowers absorption of B12, iron, magnesium and calcium carbonate. Calcium citrate is a better choice; ask about monitoring.
Water pills (furosemide, thiazides)
Furosemide-type pills wash out magnesium, zinc, thiamin and calcium. Thiazides raise blood calcium, so calcium plus vitamin D supplements need a doctor’s check.
Anti-seizure medicines (phenytoin, carbamazepine, valproate)
They can lower folate, vitamin D, vitamin K and biotin. Ask about bone health and folate, especially before pregnancy.
Steroids by mouth (prednisolone)
Long courses thin bones. Calcium and vitamin D are usually advised; your doctor will plan it.
Osteoporosis tablets (alendronate and similar)
Take on an empty stomach with plain water and wait 30–60 minutes before food, calcium or other supplements.
Digoxin (heart)
High calcium or low magnesium can affect heart rhythm with digoxin. Do not start calcium, vitamin D or magnesium without asking.
Page updated: 2026-10-08 · By Prof. E. Shalaan, Applied Sciences and AI (ASAI)