What are the instructions for taking calcium supplements for Premenstrual Dysphoric Disorder (PMDD), including timing and food intake?

Calcium Supplementation Instructions for PMDD

For calcium supplementation in PMDD, instruct her to take calcium carbonate with meals or calcium citrate with or without meals, divided into doses of no more than 500-600 mg of elemental calcium at a time, spread throughout the day. 1, 2

Timing and Food Intake

Calcium Carbonate

• Must be taken with meals to optimize absorption, as it requires gastric acid for proper absorption 1, 2
• The 40% elemental calcium content means a 500 mg tablet provides 200 mg of elemental calcium 1

Calcium Citrate

• Can be taken with or without food, as absorption is independent of gastric acidity 1, 2
• Contains 21% elemental calcium, so a 950-1000 mg tablet provides approximately 200-210 mg elemental calcium 1, 2
• Preferred option if she has any gastrointestinal symptoms or takes acid-reducing medications 2

Dosing Strategy

Divided Doses Throughout the Day

• Split the total daily dose into multiple administrations (ideally with meals and at bedtime) to maximize absorption 3, 4
• No single dose should exceed 500-600 mg of elemental calcium to minimize gastrointestinal side effects and optimize absorption 1, 2, 4
• A divided dose regimen (4 times daily with meals and at bedtime) results in substantially greater absorption than once-daily dosing 3

Total Daily Calcium Intake

• For PMDD, calcium supplementation has evidence supporting its use at 1200 mg elemental calcium per day 5
• Account for dietary calcium intake when calculating supplement needs—the total from food plus supplements should not exceed 2000-2500 mg per day 1, 2

Important Separation from Other Supplements

Iron Interaction

• Advise taking calcium and iron supplements 2 hours apart, as calcium can inhibit iron absorption 1
• This is particularly important if she is also taking iron supplements or a multivitamin containing iron 1

Common Pitfalls and Caveats

Gastrointestinal Side Effects

• Calcium carbonate is more likely to cause constipation and bloating compared to calcium citrate 2
• If she develops these symptoms with calcium carbonate, switch to calcium citrate 2

Upper Intake Limits

• Do not exceed 2000 mg per day of total calcium (from all sources combined) in women over 50 years 1
• Excessive calcium intake may increase risk of kidney stones and potentially cardiovascular events 1, 2

Medication Interactions

• If she takes proton pump inhibitors (PPIs) or H2 blockers for any reason, calcium citrate is strongly preferred as it doesn't require stomach acid for absorption 2

Practical Example

For a typical 1200 mg elemental calcium daily regimen:

• Calcium carbonate: Take one 500 mg tablet (200 mg elemental calcium) with breakfast, lunch, and dinner 1
• Calcium citrate: Take one 950-1000 mg tablet (approximately 200 mg elemental calcium) with or between meals, twice daily 1, 2