Oyster Shell Calcium/vitamin D Tabs
It is used to help growth and good health.It is used to prevent or treat soft, brittle bones (osteoporosis).It is used to treat or prevent low calcium levels.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Mineral and Vitamin Supplement
Pharmacologic Class
Calcium Supplement; Vitamin D Analog
Pregnancy Category
Category A (at recommended daily allowance); Category C (at doses exceeding RDA)
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
This product combines calcium, a mineral essential for strong bones and teeth, with vitamin D, which helps your body absorb calcium. It's commonly used to prevent or treat calcium and vitamin D deficiencies, especially for bone health.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take this medication with food as directed.
Storing and Disposing of Your Medication
Store this medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about disposal, consult your pharmacist. You may also want to check if there are drug take-back programs available in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take this medication with food as directed.
Storing and Disposing of Your Medication
Store this medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you have questions about disposal, consult your pharmacist. You may also want to check if there are drug take-back programs available in your area.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take calcium carbonate (oyster shell calcium) with food to improve absorption.
- Do not take calcium supplements at the same time as iron supplements, thyroid hormones, or certain antibiotics (like tetracyclines or fluoroquinolones); separate by at least 2-4 hours.
- Maintain a balanced diet rich in calcium (dairy, leafy greens) and vitamin D (fatty fish, fortified foods).
- Engage in regular weight-bearing exercise to support bone health.
- Limit excessive alcohol intake and smoking, which can negatively impact bone density.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
Calcium: 1000-1200 mg elemental calcium daily (often divided doses); Vitamin D: 600-800 IU (15-20 mcg) daily
Dose Range:
500 - 2500 mg
Condition-Specific Dosing:
osteoporosis_prevention:
Calcium: 1200 mg/day; Vitamin D: 800-1000 IU/day
vitamin_d_deficiency:
Vitamin D: 1000-4000 IU/day (or higher for short periods under medical supervision)
hypocalcemia:
Doses vary widely based on severity and cause, often higher than supplementation doses
Pediatric Dosing
Neonatal:
Not established (specific formulations/doses for infants, often liquid)
Infant:
Calcium: 200-260 mg/day; Vitamin D: 400 IU/day (from birth to 12 months)
Child:
Calcium: 700-1000 mg/day (1-8 years); Vitamin D: 600 IU/day (1-18 years)
Adolescent:
Calcium: 1300 mg/day (9-18 years); Vitamin D: 600 IU/day (9-18 years)
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment for supplementation, monitor calcium and vitamin D levels.
Moderate:
Use with caution. Monitor serum calcium, phosphate, and vitamin D levels closely. May require active vitamin D forms (e.g., calcitriol) instead of cholecalciferol.
Severe:
Contraindicated for cholecalciferol in severe renal impairment (CrCl <30 mL/min) due to impaired 1-alpha-hydroxylation. Active vitamin D forms are required. Calcium supplementation needs careful monitoring due to hypercalcemia risk.
Dialysis:
Calcium and vitamin D supplementation must be managed by a nephrologist. Active vitamin D forms are typically used. Avoid calcium carbonate if hyperphosphatemia is not controlled.
Hepatic Impairment:
Mild:
No specific adjustment.
Moderate:
No specific adjustment, but severe liver disease may impair 25-hydroxylation of vitamin D, potentially requiring calcifediol.
Severe:
May impair 25-hydroxylation of vitamin D. Monitor vitamin D levels and consider calcifediol if deficiency persists.
Pharmacology
Mechanism of Action
Calcium is an essential mineral for bone formation, nerve impulse transmission, muscle contraction, and blood coagulation. Vitamin D (cholecalciferol) is a fat-soluble vitamin that, after activation in the liver (to 25-hydroxyvitamin D) and kidneys (to 1,25-dihydroxyvitamin D), acts as a hormone to regulate calcium and phosphate homeostasis. It promotes intestinal absorption of calcium and phosphate, facilitates bone mineralization, and plays a role in immune function and cell growth.
Pharmacokinetics
Absorption:
Bioavailability:
Calcium: 20-40% (varies with dose, food, and individual factors); Vitamin D: ~50-80% (fat-soluble, enhanced by dietary fat)
Tmax:
Calcium: 1-2 hours (for peak serum levels after oral dose); Vitamin D: 10-24 hours (for peak serum 25-OH D levels after single dose)
FoodEffect:
Calcium carbonate (oyster shell calcium) absorption is enhanced by food due to increased stomach acid production. Vitamin D absorption is enhanced by dietary fat.
Distribution:
Vd:
Calcium: ~0.2 L/kg (extracellular fluid, bone); Vitamin D: Large Vd, stored in adipose tissue and muscle
ProteinBinding:
Calcium: ~40-50% (primarily to albumin); Vitamin D: >99% (to vitamin D binding protein)
CnssPenetration:
Limited (Calcium); Yes (Vitamin D, but not primary site of action)
Elimination:
HalfLife:
Calcium: Not applicable (homeostatically regulated); Vitamin D (cholecalciferol): ~24 hours (initial), 25-OH D: ~2-3 weeks, 1,25-OH D: ~4-6 hours
Clearance:
Not available (Calcium); Not available (Vitamin D)
ExcretionRoute:
Calcium: Primarily fecal (unabsorbed), renal (filtered and reabsorbed); Vitamin D: Primarily biliary/fecal, minor renal
Unchanged:
Not applicable (Calcium); Minimal (Vitamin D)
Pharmacodynamics
OnsetOfAction:
Gradual (weeks to months for bone health benefits)
PeakEffect:
Months (for optimal bone density and vitamin D status)
DurationOfAction:
Varies; Vitamin D stores can last for weeks to months
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Attention Immediately
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high calcium levels, including:
+ Weakness
+ Confusion
+ Feeling tired
+ Headache
+ Upset stomach and vomiting
+ Constipation
+ Bone pain
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor:
Upset stomach or vomiting
Constipation
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice about side effects.
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of high calcium levels, including:
+ Weakness
+ Confusion
+ Feeling tired
+ Headache
+ Upset stomach and vomiting
+ Constipation
+ Bone pain
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor:
Upset stomach or vomiting
Constipation
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice about side effects.
Seek Immediate Medical Attention If You Experience:
- Signs of too much calcium (hypercalcemia): severe constipation, nausea, vomiting, loss of appetite, increased thirst, increased urination, muscle weakness, fatigue, confusion, or kidney stones (back pain, blood in urine).
- Signs of vitamin D toxicity: similar to hypercalcemia, plus weight loss, irregular heartbeat.
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
Certain health conditions, including:
+ High calcium levels
+ High vitamin D levels
+ Kidney stones
+ Low phosphate levels
This list is not exhaustive, and it is crucial to discuss all your health problems with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription medications
Over-the-counter (OTC) medications
Natural products
Vitamins
It is vital to verify that it is safe to take this medication with all your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
Certain health conditions, including:
+ High calcium levels
+ High vitamin D levels
+ Kidney stones
+ Low phosphate levels
This list is not exhaustive, and it is crucial to discuss all your health problems with your doctor.
Additionally, provide your doctor and pharmacist with a comprehensive list of all the medications you are taking, including:
Prescription medications
Over-the-counter (OTC) medications
Natural products
Vitamins
It is vital to verify that it is safe to take this medication with all your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. If you have a known allergy to tartrazine (also referred to as FD&C Yellow No. 5), consult with your doctor, as some formulations of this drug may contain this ingredient.
When taking this medication, be aware that it may interfere with the absorption of other oral medications. To minimize potential interactions, your doctor may recommend taking other oral drugs at a different time than this medication. Discuss your medication schedule with your doctor to ensure safe and effective use.
Adhere to the dietary plan recommended by your doctor to maximize the benefits of this medication and minimize potential side effects.
If you are pregnant, planning to become pregnant, or are breastfeeding, notify your doctor. It is crucial to discuss the potential benefits and risks of this medication to both you and your baby, allowing you to make an informed decision about your treatment.
When taking this medication, be aware that it may interfere with the absorption of other oral medications. To minimize potential interactions, your doctor may recommend taking other oral drugs at a different time than this medication. Discuss your medication schedule with your doctor to ensure safe and effective use.
Adhere to the dietary plan recommended by your doctor to maximize the benefits of this medication and minimize potential side effects.
If you are pregnant, planning to become pregnant, or are breastfeeding, notify your doctor. It is crucial to discuss the potential benefits and risks of this medication to both you and your baby, allowing you to make an informed decision about your treatment.
Overdose Information
Overdose Symptoms:
- Severe hypercalcemia (nausea, vomiting, constipation, polyuria, polydipsia, muscle weakness, fatigue, confusion, stupor, coma)
- Kidney stones
- Kidney damage
- Cardiac arrhythmias
What to Do:
Discontinue product immediately. Seek emergency medical attention. Hydration with intravenous fluids, loop diuretics, and other medications (e.g., calcitonin, bisphosphonates) may be used to lower calcium levels. Call 1-800-222-1222 (Poison Control).
Drug Interactions
Major Interactions
- Digoxin (with hypercalcemia risk from high vitamin D doses)
- Thiazide diuretics (increased risk of hypercalcemia)
- Certain anticonvulsants (e.g., phenytoin, phenobarbital, carbamazepine - may increase vitamin D metabolism, leading to deficiency)
- Corticosteroids (decrease calcium absorption and increase vitamin D metabolism)
Moderate Interactions
- Tetracyclines (e.g., doxycycline, minocycline - calcium can chelate, reduce absorption; separate administration by 2-4 hours)
- Fluoroquinolones (e.g., ciprofloxacin, levofloxacin - calcium can chelate, reduce absorption; separate administration by 2-6 hours)
- Bisphosphonates (e.g., alendronate, risedronate - calcium can reduce absorption; separate administration by at least 30-60 minutes)
- Levothyroxine (calcium can reduce absorption; separate administration by at least 4 hours)
- Iron supplements (calcium can reduce iron absorption; separate administration by 2-4 hours)
- Orlistat (may reduce absorption of fat-soluble vitamin D)
- Cholestyramine/Colestipol (may reduce absorption of fat-soluble vitamin D)
- Mineral oil (may reduce absorption of fat-soluble vitamin D)
Minor Interactions
- Spinach, rhubarb, whole grains (contain oxalates/phytates that can reduce calcium absorption)
Monitoring
Baseline Monitoring
Serum Calcium (total and/or ionized)
Rationale: To establish baseline levels and identify pre-existing hyper/hypocalcemia.
Timing: Prior to initiation of high-dose supplementation or if deficiency is suspected.
Serum 25-hydroxyvitamin D (25-OH D)
Rationale: To assess vitamin D status and guide dosing.
Timing: Prior to initiation of supplementation, especially if deficiency is suspected.
Renal Function (BUN, Creatinine, eGFR)
Rationale: To assess kidney health, as renal impairment affects vitamin D metabolism and calcium excretion.
Timing: Prior to initiation, especially in elderly or those with risk factors for kidney disease.
Routine Monitoring
Serum Calcium (total)
Frequency: Every 3-6 months initially, then annually for long-term high-dose supplementation; more frequently if symptoms of hypercalcemia or renal impairment develop.
Target: 8.5-10.2 mg/dL
Action Threshold: >10.5 mg/dL (investigate cause, reduce dose)
Serum 25-hydroxyvitamin D (25-OH D)
Frequency: Every 3-6 months until target level achieved, then annually for maintenance.
Target: 30-100 ng/mL (75-250 nmol/L)
Action Threshold: <20 ng/mL (increase dose); >100 ng/mL (reduce dose, risk of toxicity)
Renal Function (BUN, Creatinine)
Frequency: Annually, or more frequently if risk factors for renal impairment or hypercalcemia are present.
Target: Within normal limits for age/sex
Action Threshold: Significant decline in eGFR or increase in creatinine (re-evaluate dosing, especially vitamin D)
Symptom Monitoring
- Symptoms of hypercalcemia: nausea, vomiting, constipation, polyuria, polydipsia, fatigue, muscle weakness, confusion, kidney stones.
- Symptoms of vitamin D toxicity: similar to hypercalcemia, plus anorexia, weight loss, cardiac arrhythmias.
Special Patient Groups
Pregnancy
Calcium and Vitamin D are essential nutrients during pregnancy for fetal bone development and maternal health. Recommended daily allowances should be met. High doses exceeding the upper tolerable limit should be avoided due to potential risks of hypercalcemia in the mother and fetus.
Trimester-Specific Risks:
First Trimester:
Essential for early fetal development; generally safe at RDA.
Second Trimester:
Continued importance for fetal bone mineralization; generally safe at RDA.
Third Trimester:
Increased fetal calcium demands; generally safe at RDA. High doses may pose risk of hypercalcemia.
Lactation
Calcium and Vitamin D are excreted in breast milk and are essential for the infant. Supplementation at recommended daily allowances is generally considered safe and beneficial for both mother and infant.
Infant Risk:
L1 (compatible with breastfeeding at recommended daily allowance). Excessive maternal doses could theoretically lead to hypercalcemia in the infant, but this is rare with typical supplementation.
Pediatric Use
Essential for bone growth and development. Dosing varies significantly by age and weight. Care must be taken not to exceed age-appropriate upper tolerable limits to avoid toxicity, especially with vitamin D.
Geriatric Use
Increased risk of calcium and vitamin D deficiency due to decreased dietary intake, reduced skin synthesis of vitamin D, and impaired renal 1-alpha-hydroxylation. Higher recommended daily allowances for calcium (1200 mg) and vitamin D (800-1000 IU) are common for osteoporosis prevention. Monitor renal function and calcium levels more closely.
Clinical Information
Clinical Pearls
- Oyster shell calcium is calcium carbonate, which is best absorbed when taken with food due to its reliance on stomach acid.
- For individuals with achlorhydria or taking proton pump inhibitors/H2 blockers, calcium citrate may be a better absorbed alternative.
- Divide calcium doses throughout the day (e.g., 500-600 mg per dose) as the body can only absorb a limited amount at one time.
- Vitamin D supplementation is crucial for calcium absorption and utilization, especially in individuals with limited sun exposure.
- Always check the elemental calcium content, not just the calcium salt weight (e.g., 1250 mg calcium carbonate contains 500 mg elemental calcium).
- Educate patients on symptoms of hypercalcemia to ensure early detection of potential toxicity.
Alternative Therapies
- Dietary calcium (dairy products, fortified foods, leafy greens)
- Sun exposure (for natural vitamin D synthesis)
- Prescription vitamin D (e.g., ergocalciferol, calcitriol) for severe deficiency or specific conditions
- Bisphosphonates (for osteoporosis treatment)
- Selective estrogen receptor modulators (SERMs) (for osteoporosis treatment)
- Parathyroid hormone analogs (for osteoporosis treatment)
Cost & Coverage
Average Cost:
$5 - $30 per 30-250 tablets
Generic Available:
Yes
Insurance Coverage:
Often not covered by prescription insurance as they are over-the-counter supplements. May be covered by FSA/HSA.
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide detailed information about the overdose, including the substance taken, the amount, and the time it occurred.