NEW
🌙 Magnesium
Rugby Magnesium Oxide 400 mg Tablets - Dietary Supplement…
Cost per serving
$0.04
360 servings · ~360-day supply
Low absorption
$13.90Price from Amazon.com
Rugby · Amazon.com 0
See the offer Best Magnesium for constipation
Magnesium pulls water into the bowel, which is why magnesium citrate is sold as an over-the-counter laxative. Below, the magnesium products people use ranked by real cost per dose (to the commonly-studied 300 mg dose). A value comparison, not medical advice.
Updated September 2026
What the evidence actually shows
Well established as an osmotic laxative for occasional constipation — magnesium citrate is an FDA-recognized OTC laxative ingredient. Laxative doses on those labels are far above the 350 mg/day supplement upper limit and are for short-term use. Avoid high doses with kidney disease, and ask a doctor if you need a laxative for more than a week.
How this list is built: these are magnesium products ranked by real cost per dose across our whole magnesium catalogue — not filtered or re-ordered by constipation. We don’t hold per-product evidence for a specific use, so we don’t pretend to rank for one. Products whose own label says they are for something else are left out.
Background on magnesium from the NIH Office of Dietary Supplements .
For constipation, citrate is the form usually chosen — see best citrate by cost per dose.
Ranked by cost per dose
NEW
🥤 Electrolytes
Advanced Electrolyte Complex Capsules for Hydration
Cost per serving
$0.04
240 servings · ~240-day supply
High absorption
$9.90Price from Amazon.com
Micro Ingredients · Amazon.com 0
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🌙 Magnesium
Rugby Magnesium Oxide 400 mg Tablets - Dietary Supplement…
Cost per serving
$0.05
120 servings · ~120-day supply
Low absorption
$5.98Price from Amazon.com
Rugby · Amazon.com 0
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🌙 Magnesium
Swanson Magnesium 200 Milligrams 250 Capsules
Cost per serving
$0.05
250 servings · ~250-day supply
$12.59Price from Amazon.com
Swanson · Amazon.com 0
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🌶️ Capsaicin (cayenne)
PURE ORIGINAL INGREDIENTS Cayenne Pepper (730 Capsules) No…
Cost per serving
$0.05
730 servings · ~730-day supply
$37.29Price from Amazon.com
PURE ORIGINAL INGREDIENTS · Amazon.com 0
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🦴 Calcium
Amazing Formulas Calcium Magnesium Zinc D3-300 Tablets Per…
Cost per serving
$0.05
300 servings · ~300-day supply
High absorption
$16.49Price from Amazon.com
Amazing Formulas · Amazon.com 0
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🌙 Magnesium
Nutricost Potassium (99 mg) Magnesium (210 mg) Citrates
Cost per serving
$0.06
240 servings · ~240-day supply
$13.95Price from Amazon.com
Nutricost · Amazon.com 0
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🥤 Electrolytes
Advanced Electrolyte Pills
Cost per serving
$0.06
240 servings · ~240-day supply
$13.99Price from Amazon.com
NatureBell · Amazon.com 0
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🌙 Magnesium
Magnesium Malate Capsules (420 Count) - 1,500mg Per Serving…
Cost per serving
$0.06
420 servings · ~420-day supply
$24.95Price from Amazon.com
Double Wood Supplements · Amazon.com 0
See the offer See the full ranking, benchmarks and lab-tested brands on best magnesium by cost per dose.
Frequently asked
Does magnesium help with constipation?+
Well established as an osmotic laxative for occasional constipation — magnesium citrate is an FDA-recognized OTC laxative ingredient. Laxative doses on those labels are far above the 350 mg/day supplement upper limit and are for short-term use. Avoid high doses with kidney disease, and ask a doctor if you need a laxative for more than a week. This page ranks the products people take by real cost per dose; it does not claim a supplement treats or cures anything. Not medical advice — talk to a clinician about constipation.
Which magnesium is cheapest for constipation?+
As of September 2026, the best value we track is Rugby Magnesium Oxide 400 mg Tablets - Dietary Supplement - Gluten-Free - 120 Count (3 Pack). The full ranking by cost per dose is above; for constipation, citrate is the form usually chosen. Price ÷ servings ÷ dose — the number retailers rarely divide out.