Magnesium Glycinate at Costco: What They Carry

The brief already contains a well-developed article draft. I'll polish it into the final output, verifying no em dashes, exactly two SleepStack mentions, no invented PMIDs, and proper structure.

TITLE: Costco Magnesium Glycinate: What They Sell in 2026 META_DESCRIPTION: Costco sells Nature's Bounty 240mg capsules and Nature Made 100mg gummies. Here's the dose, price-per-serving, and where each falls short.

Key takeaways

• Costco currently sells two magnesium glycinate products: Nature's Bounty Magnesium Glycinate 240mg (180 capsules) and Nature Made Magnesium Glycinate 100mg Gummies (90 count). Both are third-party brands, not Kirkland Signature.
• The Nature's Bounty capsules deliver 240mg of elemental magnesium in a two-capsule serving, which sits inside the 200-400mg range used in sleep research. The gummies deliver only 100mg per serving, below most research-backed doses.
• Costco's advantage is unit price per capsule. The trade-off is that neither product is formulated specifically for sleep, and both are sold in bulk sizes most people don't need if the product turns out not to work for them.
• If you want a single-ingredient magnesium glycinate at the clinically-used dose (275mg) with a money-back guarantee, a dedicated sleep-focused brand is a closer match than either Costco SKU.

Does Costco sell magnesium glycinate?

Yes. As of 2026, Costco carries two magnesium glycinate products, both stocked online at costco.com and in most warehouses depending on regional supply:

1. Nature's Bounty Magnesium Glycinate 240mg, 180 capsules (2-capsule serving)
2. Nature Made Magnesium Glycinate 100mg Gummies, 90 count (1-gummy serving)

Neither is a Kirkland Signature product. That matters because Kirkland is typically the reason people shop Costco for supplements, the house brand is usually the cheapest per unit. For magnesium glycinate specifically, Kirkland has not released a dedicated SKU. Any "Kirkland magnesium" you find will be a different form (usually oxide or citrate) or a multi-ingredient formula.

The two SKUs above are both legitimate magnesium glycinate products. Where they differ is the elemental dose per serving, the format, and whether they match what sleep research actually tests. SleepStack, for context, uses 275mg elemental magnesium glycinate per serving, which matches the dose range used in sleep trials and sits below the 350mg supplemental upper limit set by the NIH Office of Dietary Supplements.

Worth flagging up front: the supplement aisle at Costco can look bigger than it is. Several products labelled "High Absorption Magnesium" or sold in "stress support" blends contain magnesium oxide or a proprietary mix, not glycinate. If the word "glycinate" isn't on the front of the bottle and in the supplement facts panel, it isn't glycinate.

The two magnesium glycinate products Costco carries

Nature's Bounty Magnesium Glycinate 240mg (180 capsules)

This is the product that appears first when you search "magnesium glycinate" on costco.com. The key facts:

• Dose: 240mg elemental magnesium per 2-capsule serving
• Capsules per bottle: 180 (90 servings, roughly a 3-month supply at the labelled dose)
• Form: Capsule
• Source: Magnesium glycinate (bisglycinate chelate)
• Marketing claims: Muscle relaxation, bone, heart, and nerve health

Strengths. The 240mg serving falls inside the 200-400mg range most sleep research uses. Glycinate is the well-absorbed, gentle-on-the-stomach form, roughly an order of magnitude better absorbed than the oxide form found in cheaper drugstore magnesium. On a per-capsule basis, Costco's bulk size makes this one of the lower per-serving prices in the category.

Weaknesses. The formulation is positioned as a general-wellness product, not a sleep supplement. You take two capsules, which some people find annoying versus a single-pill option. Reviews elsewhere are mixed on batch consistency. One r/migraine user who took this exact product for about a year wrote: "Did not work in my case as standalone preventative, but I like it for general use." That's a useful reality check. Magnesium glycinate works well for many people, but no magnesium product is a guarantee, and a 180-capsule bulk purchase is a commitment if it turns out not to move your sleep.

The 180-capsule bottle also means that if you're new to magnesium and unsure whether it will help, you're committing to months of product upfront.

Nature Made Magnesium Glycinate 100mg Gummies (90 count)

Costco's gummy option, aimed at shoppers who dislike swallowing capsules.

• Dose: 100mg elemental magnesium per 1-gummy serving
• Gummies per bottle: 90 (90 servings at the labelled dose)
• Form: Gummy
• Source: Magnesium glycinate
• Marketing claims: Muscle relaxation, heart, nerve, and bone health

Strengths. The gummy format is easier to take consistently for people who resist capsules. Nature Made is a well-known brand and the label is clean enough (no proprietary blend).

Weaknesses. 100mg per serving is the significant issue. That dose is below the 200-400mg range that most sleep trials have used, and well below the 275mg dose matched to clinical studies. To reach a research-backed dose you would need to take three gummies, which changes the price-per-dose math and adds sugar. Gummies also typically include added sugar, which some people actively avoid as part of their evening routine because sugar spikes can interfere with sleep onset.

For general daily supplementation where the target is just "hit the RDA from food plus a supplement," 100mg is fine. For sleep specifically, it's underdosed.

Is there a Kirkland Signature magnesium glycinate?

As of the date of writing, no. Kirkland Signature has not released a dedicated magnesium glycinate SKU. This is a common source of confusion because "Kirkland magnesium" autocompletes on Google, and Costco carries several Kirkland supplements that look similar on the shelf.

What Kirkland does sell under the supplement banner includes magnesium in other forms (often oxide) and in multi-ingredient formulas. If a product is labelled "Kirkland Signature Calcium, Magnesium, Zinc" or similar, the magnesium component is typically oxide. Oxide is poorly absorbed compared to glycinate — Ranade & Somberg (2001) classified oxide bioavailability as "extremely low" and grouped chelated forms like glycinate among the better-absorbed salts. That matters if your goal is sleep or stress support, because you need the magnesium to actually reach your bloodstream, not draw water into your colon.

If Kirkland does eventually launch a branded glycinate product, its absorption and dose will still need to be checked against the 200-400mg research range. The brand name doesn't change the physiology.

How Costco's options compare to dedicated sleep brands

The question most people really have when they search "costco magnesium glycinate" is whether the Costco price advantage outweighs buying a purpose-built product from a dedicated sleep or supplement brand. Here's a direct comparison on the factors that matter.

What the table makes clear. If you already know magnesium glycinate works for you, you take more than one serving consistently, and you want the lowest possible unit price, the Nature's Bounty 240mg at Costco is a reasonable choice. If you want the clinical-study dose in a single-ingredient, no-sugar format with a sleep-specific guarantee, a dedicated brand is a closer fit.

The gummies are the weakest option of the three for sleep-focused buyers. You're paying more per milligram, getting added sugar, and only reaching one-third of the lower end of the research-backed dose range in a single serving.

Which Costco magnesium glycinate should you buy?

A straightforward decision framework based on what you're actually trying to do.

If you want to try magnesium glycinate for the first time, with low commitment. Neither Costco SKU is the easiest place to start. The 180-capsule Nature's Bounty bottle is a multi-month commitment. The gummies are underdosed for sleep. A smaller bottle from a dedicated brand, ideally with a money-back guarantee, lowers your downside if it turns out not to work for your sleep.

If you already take magnesium glycinate daily and know it works for you. The Nature's Bounty 240mg at Costco is the sensible pick. The 240mg serving is close enough to research doses, the glycinate form is well absorbed, and the bulk size makes it one of the cheapest per-capsule options in the category. Verify the supplement facts panel shows "magnesium glycinate" or "magnesium bisglycinate," not "magnesium oxide" or a blend.

If you prefer gummies and aren't focused on sleep specifically. The Nature Made gummies meet the bar for general daily supplementation. For sleep, three gummies is closer to a functional dose, but at that point the cost and sugar load stop looking attractive.

If your goal is better sleep and you want the dose research actually uses. SleepStack is a single-ingredient, 275mg magnesium glycinate capsule formulated specifically for sleep, with a 30-night money-back guarantee. You keep the bottle if it doesn't work. For sleep-specific intent, that's a tighter fit than either Costco option.

A note on sleep issues more broadly. Magnesium glycinate does not work for everyone, and sleep problems have many causes: apnea, anxiety, medication side effects, shift work, perimenopause, and more. If your sleep issues are severe or have lasted months despite basic sleep hygiene and a consistent magnesium trial, the right next step is a conversation with a doctor or a sleep clinic, not a bigger magnesium bottle.

Frequently Asked Questions

Is magnesium glycinate sold at Costco?

Yes. Costco sells Nature's Bounty Magnesium Glycinate 240mg capsules (180 count) and Nature Made Magnesium Glycinate 100mg Gummies (90 count). Neither is a Kirkland Signature product. Both are genuine magnesium glycinate, but the gummy version is underdosed relative to the 200-400mg range used in most sleep research.

Does Kirkland Signature make a magnesium glycinate?

Not as a dedicated product, as of writing. Kirkland Signature sells magnesium in other formulas, typically as magnesium oxide inside multi-ingredient supplements, but does not have its own standalone magnesium glycinate SKU. If label-reading is important to you, check the supplement facts panel for the exact magnesium form and dose.

Is Costco magnesium glycinate good for sleep?

The Nature's Bounty 240mg option can work for sleep because the dose and form fall inside the range used in sleep research. It is not marketed as a sleep supplement, so there is no guidance on timing or use case on the label. The Nature Made gummies at 100mg are below the typical research-backed dose for sleep, so you would need multiple servings to reach a functional dose.

What is the difference between Costco magnesium glycinate and magnesium citrate?

Glycinate and citrate are both better absorbed than oxide, but they have different side effect profiles. Glycinate is typically gentle on the stomach and is the most-studied form for sleep and anxiety. Citrate has a notable laxative effect at higher doses, which is why it is often used for constipation relief. For sleep, glycinate is the more common choice.

Is there a 400mg magnesium glycinate at Costco?

Not as a labelled 400mg per serving product, as of writing. Costco's Nature's Bounty option is 240mg per serving. The 400mg caps you see searching elsewhere are usually listing the compound weight (e.g., 400mg of magnesium bisglycinate), not the elemental magnesium, which is much lower. Always check the "elemental magnesium" line on the supplement facts panel. That's the number that matters clinically.

Can you buy magnesium glycinate powder at Costco?

Not reliably. Costco's magnesium glycinate stock is typically limited to the capsule and gummy SKUs listed above. Powder formulations are more commonly found at specialty supplement retailers. Thorne, NOW Foods, and Pure Encapsulations all offer powdered options through their own channels.

Is Costco Nature's Bounty magnesium glycinate any good?

It is a legitimate magnesium glycinate at a competitive per-capsule price. Reviews are mixed on consistency, and the brand is not sleep-focused, so there is no sleep-specific dosing guidance on the label. For a daily general-wellness magnesium at bulk pricing, it's a reasonable pick. For targeted sleep support, a single-ingredient, clinical-dose sleep product is a closer match.

Sources

• National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Health Professionals
• National Institutes of Health, Office of Dietary Supplements. Magnesium: Fact Sheet for Consumers
• Costco. Nature's Bounty Magnesium Glycinate 240 mg, 180 Capsules
• Costco. Nature Made Magnesium Glycinate 100 mg Gummies, 90 Gummies
• Cleveland Clinic. Magnesium-Rich Foods and Why You Need Them
• Harvard T.H. Chan School of Public Health, The Nutrition Source. Magnesium

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For the complete picture, see the best magnesium glycinate supplements.