Magtein for Dry Eyes: What the Evidence Supports

Magtein is a branded form of magnesium L-threonate, an oral supplement marketed for cognition and sleep—not an established treatment for dry eye. Research on cognition and sleep does not establish that it restores tears or relieves dry-eye symptoms. If burning or fluctuating blur is your main concern, it makes more sense to address the eye problem directly than to choose a supplement based on brain-health claims. (Magtein ingredient information, human clinical trial)

What is Magtein?

Magnesium L-threonate combines magnesium with L-threonate. Magtein is the trademarked ingredient used in supplements sold by different brands; it is not the name of one standard capsule or serving size. The ingredient supplier describes its proposed ability to raise brain magnesium as supported by preclinical research, meaning research before human clinical testing. It also notes that this mechanism has not been directly measured in its human trials. That claim does not establish a benefit for the eye’s tear film. (Supplier information)

Magnesium itself is an essential nutrient involved in normal nerve and muscle function. Meeting a nutritional need, however, is different from treating dry-eye disease. (NIH magnesium fact sheet)

Does the research support taking it for dry eye?

There are two different questions here: whether magnesium intake is associated with eye health, and whether taking Magtein improves dry eye.

A 2024 analysis of Korean women aged 40 and older reported an association between higher dietary magnesium intake and lower dry-eye prevalence. It used survey data and a 24-hour food recall—not a trial assigning people to Magtein. An association cannot establish that a magnesium supplement prevents or treats dry eye, or identify an effective dose. (Original dietary study)

A six-week Magtein trial enrolled 100 adults aged 18–45 who reported dissatisfied sleep. It found greater improvement in some cognitive measures and one measure of sleep-related impairment, but no between-group improvement in sleep outcomes measured by a wearable ring. It did not test dry-eye symptoms, tear production or tear-film stability. Threotech funded the trial, supplied the product and helped conceptualize its design. These results are not evidence of dry-eye relief. (Original Magtein trial)

There is no established Magtein dose or treatment timeline for dry eye. A dose studied for sleep or cognition should not be repurposed as an eye-treatment recommendation.

Read the magnesium amount—not just the large number

The weight of magnesium L-threonate is not the same as the amount of magnesium it supplies. According to the supplier, 2,000 mg of Magtein provides at least 144 mg of elemental magnesium—the actual magnesium content. On a U.S. Supplement Facts panel, the line labeled “Magnesium” declares elemental magnesium. Check the serving size as well as that number. (Magtein dose information, NIH label explanation)

Before using it for any reason:

• Check kidney health. Impaired kidney function increases the risk of magnesium building up to toxic levels. If you have kidney disease, ask your clinician before taking it.
• Count other magnesium products. The U.S. upper limit for healthy adults is 350 mg of elemental magnesium daily from supplements and medicines, excluding magnesium naturally present in food and beverages. This is not a target dose; higher supplemental doses need clinician guidance.
• Check medicine interactions. Magnesium can reduce absorption of oral doxycycline, certain other antibiotics and oral osteoporosis medicines. Ask a pharmacist about spacing rather than taking them together.
• Watch for digestive effects. Supplemental magnesium can cause diarrhea, nausea and abdominal cramps.

These are magnesium-class precautions, not proof that every Magtein product has the same safety profile. (NIH safety and interaction guidance)

What to prioritize for uncomfortable eyes

For mild dry eye, artificial tears are a common first treatment. Screen breaks, avoiding direct airflow and managing dry indoor air may also help. Persistent symptoms deserve an eye examination because treatment depends on whether the problem involves tear production, evaporation, eyelids or another cause. (National Eye Institute guidance)

Our guide to choosing dry-eye drops explains liquids, gels, preservatives and contact-lens compatibility. If nutrition is a concern, magnesium-rich foods include nuts, seeds, beans, leafy greens and whole grains; discuss suspected deficiency with a qualified health professional rather than inferring it from eye discomfort alone. (NIH magnesium guidance)

Seek same-day eye care for sudden vision changes, eye pain or new light sensitivity. Sudden loss of vision needs emergency care. Do not wait to see whether a supplement helps. (Urgent eye-symptom guidance)