Calcium Carbonate: Drug information

Pharmacologic Category

  •         Antacid
  •         Antidote
  •         Calcium salt
  •         Electrolyte Supplement oral
  •         Phosphate Binder


Dosage for Adults for various concerns :


Note: 1gm of calcium carbonate is equal to 400mg of elemental calcium.


  1.       Antacid – Oral: Normally, it is advised to take 1 to 4 tablets as symptoms occur. Maximum is recommended to take 8 gm per day as calcium carbonate for up to two weeks.


Over-the-Counter dosing recommendations may differ by product and/or manufacturer, and specific product labelling should be consulted.


  1.       Calcium supplementation (OTC labelling): Orally, it is advised to take 500mg or 4 gm per day as calcium carbonate (equal to 200 mg to 1.6 g of elemental calcium) in 1:3 divided doses.


Note: The advocated daily intake of elemental calcium (from the dietary sources and additional sources if required) for optimal health of your bones is 1.2g per day (for women post-menopause) or 1 to 1.2 g per day in other adults.


It is desirable to obtain these daily amounts primarily through dietary sources. There is no documentation that the intakes higher than those recommended improve the strength of the bone.


  1.       Hyperphosphatemia in Chronic Kidney disease ( off-label usage):

Oral: Total dose of elemental calcium (including dietary sources and calcium-based phosphate binders) should not go beyond 2 gm per day.


  1.       Hypoparathyroidism (management of chronic hypocalcemia) (off-label usage):

Oral: 500 mg to 1 g of elemental calcium consumed 2 to 3 times a day. However, the required dose can vary greatly and may be required for more frequent dosing.


Note: IV calcium may be administered in acute hypocalcemia with corrected calcium less than 7mg per dL [less than or equal to 1.75mmol per L] or in severely chronic patients, e.g. those patients with arrhythmias, broncho-or laryngospasm, tetany, seizures) 


  1.       Concomitant therapy: Significant drug interactions persist, requiring dose per frequency adjustment or avoidance. It is advisable to consult the drug interaction database for any further additional information.


  1.       Renal Impairment: Dose for adult: Crcl<25mL per minute: Dosage adjustments may be required based on serum calcium levels.


Dosage considerations: 1g calcium carbonate is equal to elemental calcium of 400mg, which is further equivalent to calcium 20mEq which is again comparable to calcium 10mmol


Administration Adult: Oral: Administer with food. Doses > 600 mg (elemental calcium) per day should be divided for optimal absorption. One can swallow the whole capsules or have them after opening them and mix the contents with the food or any drink.




Food interactions


Food may enhance calcium absorption. Calcium may reduce the absorption of iron. Bran, foods that are high in oxalates or whole-grain cereals may decrease the absorption of calcium.


Consideration of the diet: It is advisable to take calcium carbonate with food. Also, it is recommended to limit the intake of bran, foods with high oxalates, or whole-grain cereals that may reduce calcium absorption.


Reference range:


Calcium supplementation:


Serum calcium: 8.5 to 10.5 mg per dL (2.12 to 2.62 mmol/L)


Due to the poor interaction between the serum iodized calcium (free) and total serum calcium, especially in low albumin or acid to base imbalances, direct measurement of ionized calcium is advised.


In the state of low albumin, the corrected total serum calcium may be evaluated by:


Corrected total calcium (mg per dL) = measured serum calcium (mg/mL) + 0.8 (4-measured serum albumin [g/dL])




Corrected total calcium (mmol per L) = measured serum calcium (mmol/L) +0.02 (40-measured serum albumin [g/L])


Hypoparathyroidism – Calcium supplementation –

Correct serum calcium to low- normal range or no more than 0.5mg per dL below normal; calcium-phosphate product less than 55 mg²/dL²


Calcium (total): Adults: 9 to 11mg/dL (2.05 to 2.54 mmol/L), may slightly reduce with age. Avoid hypercalcemia for chronic kidney ailment (CKD) stages G3a to G5D


Phosphorus: 2.5 to 4.5 mg per dL (0.81 to 1.45 mmol/L). Lower elevated phosphorous levels towards the normal range for CKD stages G3a to G5D.




CKD stage G3a to G5: Here, the optima PTH level is unknown, so it is essential to evaluate the patients with constantly elevated intact PTH levels or if levels are regularly moving above the normal range 


Dialysis patients: Maintain intact parathyroid hormone (iPTH) within 2 to 9 times the upper limit of normal.


 Some of the  Indian brands:

  1. 4 bone
  2. Shelcal
  3. Cipcal
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