8 Factors That Affect How Long Magnesium Citrate Stays in Your System

The time it takes for your body to clear magnesium citrate varies. It depends on the dose, formulation, and other factors that enhance or inhibit magnesium absorption.

1. Your Individual Magnesium Status

How much magnesium your body absorbs may depend on your current levels. If you’re deficient, your body may work harder to hold on to it, absorbing more from your intestines and urine. The right supplement, such as magnesium citrate, can help bring your levels back up.

2. The Type of Magnesium You Take

The type of magnesium you take affects how well it’s absorbed, and that may influence how long it stays in your system.

For example, organic forms of magnesium (like magnesium citrate) tend to be absorbed more easily than inorganic forms (like magnesium oxide).

Magnesium citrate tablets, capsules, and softgels can replenish magnesium levels. Constipation treatments (i.e., magnesium citrate solution) are not intended to help replenish levels.

3. Any Health Conditions You May Have

Health conditions and lifestyle factors can disrupt magnesium balance by lowering absorption or increasing loss. This may impact how long magnesium stays in your system or cause it to build up.

• Vitamin D deficiency reduces magnesium absorption.
• Diarrhea and vomiting remove magnesium from your body.
• Gastrointestinal diseases like celiac disease, Crohn’s disease, and colitis can lead to low magnesium levels due to chronic diarrhea.
• Diabetes mellitus/insulin resistance may cause high blood sugar levels in the kidneys, leading to more magnesium loss through your urine.
• Alcohol use disorder may cause decreased dietary intake, gastrointestinal problems, vomiting, phosphate depletion, kidney dysfunction, and vitamin D deficiency. These can all contribute to magnesium deficiency.
• Kidney disease, particularly in severe cases, can increase the risk of high magnesium levels as the body has difficulty getting rid of excess magnesium.

4. How Much Magnesium Citrate You Take

The amount of magnesium citrate you take may directly impact how long it stays in your body. Larger doses aren’t always better; your body may absorb less when taking too much at once.

• Magnesium absorption decreases with higher dosages. Your body may absorb less magnesium citrate as you take more.
• Smaller, more frequent dosages may improve absorption. Magnesium uptake is higher when taken in multiple low doses throughout the day than when taken in a single large dose.
• Absorption rates may vary significantly by dosage size. One study showed that 65% of magnesium was absorbed from a daily dose of 36 milligrams (mg), whereas only 11% was absorbed from a daily dose of 973 mg.
• Be aware of your daily needs. Adult males need 400 to 420 mg of magnesium a day. Adult females need 310 to 320 mg a day.
• Too much magnesium from dietary supplements—over 350 mg per day for adults—can cause diarrhea, nausea, and stomach cramps.

5. Medications You Take

Some medications may interfere with how your body absorbs or eliminates magnesium citrate. This may shorten or extend the time magnesium stays in your system.

Medications that reduce magnesium levels include the following:

• Antibiotics: Amoxicillin, Zithromax (azithromycin), Vibramycin (doxycycline), levofloxacin, Cipro (ciprofloxacin), aminoglycoside antibiotics
• Proton pump inhibitors: Prilosec (omeprazole)
• Blood pressure medications: Apresoline (hydralazine) plus ACE inhibitors (e.g., Zestril or lisinopril) with hydrochlorothiazide
• Diuretics or water pills: Lasix (furosemide)
• Histamine-2 receptor blockers: Pepcid (famotidine)
• Corticosteroids: Decadron (dexamethasone), Deltasone (prednisone)
• Estrogens: estradiol and estrogen-containing medications
• Seizure medications: Dilantin (phenytoin), phenobarbital
• Heart medications: Pacerone (amiodarone)
• Immunosuppressants: Neoral (cyclosporine), Prograf (tacrolimus)
• Stimulants: Ritalin (methylphenidate)

6. Other Supplements You Use

Some supplements may interfere with magnesium absorption, especially in high doses. This may affect how much magnesium citrate your body retains, and for how long:

• Calcium
• Copper
• Iron
• Manganese
• Phosphorus
• Zinc

7. Specific Foods You Eat

What you eat can affect how much magnesium citrate your body absorbs and how quickly it may eliminate it. Some foods block absorption, while others may speed up magnesium loss.

Specific foods decrease magnesium absorption: 

• Oxalate-containing foods: spinach, cabbage, broccoli, Brussels sprouts
• Phytate-containing foods: bran and whole-meal bread
• Partly and non-fermentable fibers: wheat bran, as well as hemicellulose, cellulose, and lignin found in specific grains, fruits, and vegetables

Dietary patterns and drinks may increase magnesium removal by your kidneys:

8. Your Age

As you age, changes in your body and diet may make it more challenging to keep magnesium levels steady. This may impact how long magnesium citrate stays in your system.

Deficiency risk may increase with age due to the following:

• Lower magnesium intake
• Decreased absorption
• Increased kidney excretion

How Your Body Handles Magnesium

To understand how long magnesium citrate stays in your body, it helps to know how your body absorbs, stores, and eliminates magnesium.

• Your body quickly absorbs magnesium. After taking magnesium, your small intestine absorbs it within about an hour. Your body absorbs about 80% of magnesium after six hours.
• Your body tightly regulates magnesium levels through your intestines, bones, and kidneys.
• Your bones and tissues are primary storage sites. About half of magnesium is stored in your bones, which release magnesium into your blood if your levels are low. The rest mostly stays in your muscles and soft tissues, while less than 1% is in your blood.
• Your body eliminates any excess magnesium through your urine.

How long magnesium citrate stays in your body depends on several factors.