Calcium Carbonate + Vitamin B12 (Methylcobalamin) + Vitamin D3 (Cholecalciferol) is a nutritional supplement containing an essential calcium source (calcium carbonate), cholecalciferol (Vitamin D3), and cyanocobalamin or methylcobalamin (Vitamin B12). It helps support bone mineralisation, nerve function, and red blood cell formation. This combination is commonly prescribed for osteoporosis, osteomalacia, rickets, and nutritional anaemia with neuropathy. Postmenopausal women and pregnant or lactating women are often prescribed this supplement. Vitamin D3 improves the absorption of calcium in the intestines, while Vitamin B12 supports the functioning of the nervous system and haematopoiesis (blood cell production), making this the best option to tackle all three deficiencies if they coexist.

Calcium Carbonate + Vitamin B12 (Methylcobalamin) + Vitamin D3 (Cholecalciferol) is a combination of three essential micronutrients which act on bone, nerve, and blood cell health. Calcium carbonate provides approximately 40% elemental calcium by weight and is required for bone mineralisation, muscle contraction, nerve signalling, hormone secretion, and blood clotting. It requires an acidic stomach environment for dissolution, which is why it is best taken with meals.

Cholecalciferol (Vitamin D3) is first hydroxylated in the liver to 25-hydroxyvitamin D [25(OH)D], then in the kidney to the active hormone calcitriol [1,25-dihydroxyvitamin D]. Calcitriol increases calcium and phosphate absorption in the gut, helps the kidneys retain calcium, and keeps parathyroid hormone in check. Without adequate Vitamin D, only about 10% to 15% of dietary calcium is absorbed, and with it, the absorption rises to roughly 30% to 40%.

Vitamin B12 (cyanocobalamin or methylcobalamin) is a cofactor for two key enzymes, methionine synthase and methylmalonyl-CoA mutase. Vitamin B12 deficiency causes megaloblastic anaemia and degeneration of the spinal cord, which may result in numbness, tingling, gait disturbance, and cognitive changes.

By combining these three nutrients, Calcium Carbonate + Vitamin B12 (Methylcobalamin) + Vitamin D3 (Cholecalciferol) addresses the frequently overlapping deficiencies seen in older adults and in people with malabsorption, where low calcium, low Vitamin D, and low B12 coexist.

Osteoporosis and osteopenia

As adjunct supplementation alongside primary osteoporosis therapy (bisphosphonates, denosumab, or other agents) for adequate bone mineralisation.

Vitamin D deficiency and insufficiency

Restores 25(OH)D levels and improves calcium absorption.

Vitamin B12 deficiency

Corrects megaloblastic anaemia and peripheral neuropathy in dietary, age-related, or drug-induced deficiency.

Osteomalacia and rickets

Corrects defective bone mineralisation caused by calcium and Vitamin D deficiency.

Hypoparathyroidism and latent tetany

Helps maintain serum calcium in people with low Parathyroid (PTH) activity.

Nutritional supplementation

For pregnant or lactating women, postmenopausal women, older adults, strict vegetarians, and those with limited sun exposure.

• Supports bone mineral density and may reduce fracture risk

• Corrects the commonly coexistent triad of calcium, Vitamin D, and Vitamin B12 deficiency in a single tablet

• Reduces paraesthesia (pin & needle), cramps, and fall risk in older adults

• Supports the formation of red blood cells people with vitamin B12-deficient anaemia

• Vitamin D3 (cholecalciferol) raises serum 25(OH)D more effectively and for longer time

• Generally well tolerated when taken with meals

Common

• Constipation, bloating, gas, or abdominal discomfort
• Nausea or mild dyspepsia
• Belching (due to carbon dioxide released when calcium carbonate reacts with stomach acid)
• Dry mouth or metallic taste

Uncommon

• Hypercalcaemia (high blood calcium), particularly with excessive dosing or concurrent high-dose Vitamin D
• Hypercalciuria (high urinary calcium), which may raise the risk of kidney stones in susceptible people
• Headache, drowsiness, or fatigue
• Skin rash or itching (hypersensitivity)

Serious side effects requiring immediate attention

• Severe hypercalcaemia, which may present as persistent nausea, vomiting, severe constipation, confusion, excessive thirst, frequent urination, or muscle weakness
• Anaphylaxis or severe allergic reaction (rare)
• Milk-alkali syndrome with very high calcium and alkali intake, which manifests as hypercalcaemia, metabolic alkalosis, and/or renal impairment
• Signs of Vitamin D toxicity with prolonged high doses, which include weight loss, polyuria, & cardiac arrhythmias

Take orally, preferably with or immediately after a meal to maximise calcium absorption. Swallow tablets whole with a glass of water. Chewable or dispersible forms should be taken exactly as described on the label. Do not exceed the prescribed dose. Maintain adequate hydration. Space this supplement at least 2 hours away from iron supplements and oral antibiotics (tetracyclines, fluoroquinolones), at least 2 hours away from oral bisphosphonates, and at least 4 hours away from levothyroxine.

In the acidic environment of the stomach, calcium carbonate dissolves, releasing ionised calcium (Ca2+). Ca2+ is absorbed in the small intestine by Vitamin D-dependent active transport (in the duodenum and jejunum) and by passive paracellular diffusion (throughout the small bowel). Once in the blood, calcium is deposited in bone (as hydroxyapatite). It helps in muscle contraction, nerve conduction, and clotting, and is regulated by PTH, calcitonin, and Vitamin D.

Cholecalciferol is hydroxylated in the liver by CYP2R1 to 25-hydroxyvitamin D, the major circulating form and the marker used to assess Vitamin D status. In the kidney, CYP27B1 converts it to 1,25-dihydroxyvitamin D (calcitriol), the active hormone. Calcitriol binds the Vitamin D receptor in the intestine, bone, and kidney to increase calcium absorption, mobilise stored calcium when needed, and reduce calcium loss in urine. It also suppresses PTH secretion, preventing secondary hyperparathyroidism and reducing bone resorption.

Vitamin B12 is needed for the functioning of two key enzymes: methionine synthase, which recycles homocysteine into methionine, and methylmalonyl-CoA mutase, which helps the body complete the metabolism of certain fats and amino acids. When a person is vitamin B12 deficient, both pathways fail, resulting in homocysteine and methylmalonic acid accumulation. This also causes DNA synthesis impairment (causing megaloblastic anaemia), and the myelin sheath around peripheral nerves and the spinal cord begins to break down.

• High-fibre or high-oxalate foods (CAUTION): Foods like bran, spinach, and wheat bran can get attached to calcium and reduce its absorption. Space these from the supplement by at least 2 hours.

• Caffeine (MODERATE): Heavy caffeine intake (>400 mg/day) modestly increases urinary calcium loss.

• Alcohol (MODERATE): Chronic heavy use reduces calcium absorption and impairs Vitamin D metabolism.

• Dairy and calcium-fortified foods (BENEFICIAL with caution): Help meet daily calcium needs, but total calcium (diet plus supplement) should not exceed 2,000–2,500 mg/day in adults.

• Grapefruit juice (CAUTION): May alter Vitamin D metabolism in some people. Take supplements after a few hours.

Levothyroxine

MODERATE–SEVERE

Calcium binds to levothyroxine in the gut, reducing absorption by up to one-third. Separate by at least 4 hours.

Bisphosphonates (alendronate, risedronate)

SEVERE

Calcium chelates bisphosphonates, lowering their absorption. Separate by at least 2 hours.

Tetracyclines and fluoroquinolones

MODERATE

Calcium forms insoluble complexes, reducing antibiotic absorption. Separate by at least 2–4 hours.

Iron supplements

MODERATE

Calcium reduces non-haem iron absorption. Separate by at least 2 hours.

Thiazide diuretics

CAUTION

Reduces urinary calcium excretion, raising serum calcium.

Proton pump inhibitors (omeprazole, pantoprazole)

MODERATE

Reduce gastric acidity and may reduce both calcium carbonate dissolution and dietary B12 absorption.

Metformin

CAUTION

Long-term use can reduce B12 absorption.

Digoxin

CAUTION

Hypercalcaemia from overuse may lead to digoxin toxicity and arrhythmias.

Anticonvulsants (phenytoin, phenobarbital, carbamazepine)

CAUTION

Speeds up Vitamin D metabolism, increasing the requirement.

Corticosteroids (prolonged use)

CAUTION

Reduce calcium absorption and increase bone loss.

Chloramphenicol

CAUTION

May interfere with the haematopoietic response to Vitamin B12.

• Chronic kidney disease (CAUTION): Calcium and Vitamin D intake must be monitored to avoid vascular and soft-tissue calcification.

• Sarcoidosis and other granulomatous diseases (AVOID): Macrophages in granulomas produce calcitriol without any regulation, increasing the risk of hypercalcaemia.

• Primary hyperparathyroidism (AVOID): Increased risk of hypercalcemia as serum calcium is already elevated.

• History of calcium-containing kidney stones (USE WITH CAUTION): Increased risk of stone formation.

• Achlorhydria or long-term PPI use (CAUTION): Reduced stomach acid impairs calcium carbonate absorption.

Excess calcium intake may cause hypercalcaemia and present as persistent nausea, vomiting, severe constipation, abdominal pain, excessive thirst, frequent urination, muscle weakness, confusion, and cardiac arrhythmias (in severe cases). Prolonged high-dose vitamin D can cause hypercalcaemia, hypercalciuria, kidney stones and/or renal impairment. Milk-alkali syndrome may develop with very large daily intakes of calcium carbonate. Vitamin B12 has no well-defined toxicity at supplemental doses, though rare allergic reactions have been reported. If overdose is suspected, stop the supplement immediately, increase oral fluid intake, and seek emergency medical care.

Take the missed dose as soon as you remember on the same day, with food if possible. If it is near the next dose, skip the missed one and resume your normal schedule. Do not take two doses at once to make up for a missed dose, as this can cause hypercalcaemia and gastrointestinal upset.