Find the Right Magnesium for Your Body in Under 2 Minutes

USP stands for United States Pharmacopeia — a nonprofit that sets purity, identity, and quality standards for ingredients used in medicines and supplements. When a magnesium product is labeled USP grade, it has been tested and verified to meet those pharmaceutical-level standards. Most magnesium sold online is food grade, which has looser specifications. USP grade is the same purity benchmark used in medical-grade formulations.

For most healthy adults, magnesium is generally well-tolerated as part of a daily routine, and many people use it that way. The right amount and form depend on your individual needs, so we recommend following label directions and starting with a smaller amount to see how your body responds. If you have a medical condition, take prescription medications, or are pregnant or nursing, talk to your healthcare provider before starting any new magnesium routine.

They’re two different magnesium compounds. Magnesium chloride has a higher concentration of elemental magnesium and is typically preferred for oral use (USP powder) or transdermal use (bath flakes, oil spray). Magnesium sulfate — better known as Epsom salt — has a lower magnesium concentration but is less expensive and more versatile, traditionally used in baths and foot soaks. Many people keep both on hand for different purposes.

Magnesium can interact with certain medications, including some antibiotics, blood pressure medications, diuretics, and osteoporosis treatments. Because the right answer depends on your specific prescriptions and health history, please talk to your doctor or pharmacist before starting any magnesium product. We’re not in a position to give individual medical advice — your healthcare provider is.

A mild tingle on first application is common and not a cause for concern — it’s often more noticeable when your skin is dry or your magnesium levels are low. The sensation typically fades within a few minutes and most people stop noticing it after a week or two of regular use. If you find it uncomfortable, dilute the spray with water 1:1 or apply it to slightly damp skin after a shower. Avoid use on broken skin or freshly shaved areas.

Most magnesium brands on Amazon source bulk powder from overseas manufacturers and relabel it under their own brand. We don’t. Greenway has manufactured in California since 1989, our magnesium chloride is USP pharmaceutical grade rather than food grade, and every batch is produced and packaged in our own FDA-registered facility. We test selected products for heavy metals (lead, cadmium, arsenic, mercury) and document the work.

Yes — selected products are tested for the four heavy metals of regulatory concern: lead, cadmium, arsenic, and mercury. For more on what these limits mean and how they’re defined, see the AAPFCO heavy metals reference at aapfco.org/metals.html. Check individual product pages for the specific testing details that apply to each item.

All of our magnesium products are manufactured and packaged at our family-owned FDA-registered facility in Madera, California — in the foothills of the Sierra Nevada. Greenway has operated as a family business since 1989, and we’re still hands-on with every batch we produce.

We stand behind every product we make. If you’re not satisfied, contact us within 30 days of delivery and we’ll work with you on a return or replacement. Reach our team at questions@greenwaybiotech.com or (562) 351-5168, Monday–Friday, 7 AM–5 PM PST.

We recommend talking to your OB-GYN, midwife, or healthcare provider before using any magnesium product during pregnancy or while nursing. Individual circumstances vary, and your provider knows your full health picture. We’re a manufacturer, not a medical advisor — please defer to your care team on this.