Alpha-GPC (L-alpha-glycerylphosphorylcholine) is a choline compound sold for focus and workout power. It is about 40.5 percent choline by weight, and the trials behind it are small and short. Labels are also confusing: some list 600 mg of a 50 percent powder, which is 300 mg of alpha-GPC.
We compared 12 alpha-GPC products on Amazon US and ranked five on dose, how clearly the label states the active amount, testing we could confirm, cost and marketing, using the same scoring as our choline supplement ranking. For the stroke study and the trials in depth, see our alpha-GPC evidence review.
The short version
- Best overall: Momentous, the only single-ingredient alpha-GPC with a contents certification we could confirm (NSF Certified for Sport), at 300 mg a day, though it has the highest daily cost.
- Lowest cost: BulkSupplements powder (the lowest daily cost for 300 mg) or Type Zero capsules (the lowest capsule cost per 300 mg, at the label's 600 mg a day).
- Read the purity line. "600 mg of Alpha GPC 50%" means 300 mg of alpha-GPC; many labels we checked state no purity at all.
- The benefit trials are tiny. Trials in healthy people were small (7 to 48 people) and short (one dose to two weeks), and most were funded by ingredient makers.
- Safety: a study of 12 million Korean adults aged 50 and over linked prescription alpha-GPC with about 43 percent more strokes; it cannot show cause, but ask a doctor first if you are over 50 or have heart or stroke risk factors.
How we ranked them
To qualify, a product needed alpha-GPC as its main ingredient, a readable Supplement Facts panel, and the brand, its own seller account, its parent company or Amazon as the seller. We left out one low-cost product whose Amazon seller name did not match the company on its label. Scoring, the same as in our choline ranking:
- Dose match (20%). Directions that give 250 to 630 mg of active alpha-GPC a day, within the doses used in healthy-adult trials.
- Evidence (15%). The same for every product here, since all are alpha-GPC.
- Label transparency (20%). Highest when the panel shows the purity or carrier, so the active amount is clear.
- Verification (15%). Full marks only for a contents certification we confirmed on the certifier's own site.
- Cost (15%), per day at the label's lowest dose, from Amazon prices when we reviewed the products.
- Formulation (5%), the same for all five (no added actives), and marketing (10%). Points off for claims beyond the evidence, absorption overreach, unverifiable superiority and listings that contradict their labels.
What alpha-GPC can and cannot do
Focus and power: small, short trials. Single-ingredient trials in healthy people enrolled 7 to 48 people and lasted from one dose to two weeks; the one that compared doses found 250 mg a day no worse than 500 mg. Most found a short-term change on one measure (lower-body force, growth hormone after a single dose, or one thinking test) but not on the others, and one, a conference poster, found no effect. Most were funded by companies selling AlphaSize or GeniusPure. We found no trial that tested months of use or showed more muscle or strength.
Dementia research is drug research. In South Korea and some European countries alpha-GPC is a prescription drug, and much of its research used about 1,200 mg a day in people with diagnosed dementia. Those results do not show what a supplement does for a healthy person, and alpha-GPC is not a treatment for any disease.
The stroke question. A 2021 study of 12,008,977 Korean adults aged 50 and over found that people prescribed alpha-GPC had about 43 percent more strokes than matched non-users (hazard ratio 1.43), roughly 16 versus 11 per 1,000 people per year. Before matching, users were older and sicker, and in Korea it was often prescribed for memory complaints and early signs of poor blood flow in the brain, so the study cannot show cause. A 2025 Korean study in people with mild memory problems did not find higher stroke risk. The idea that alpha-GPC raises stroke risk through TMAO, a gut-made compound, rests on two tiny human studies that disagree and a mouse study.
Choline. At 40.5 percent choline, 300 mg of alpha-GPC gives about 120 mg of choline and 600 mg about 243 mg, against an Adequate Intake of 425 mg for women and 550 mg for men. If you mainly want choline, a choline salt costs less; see our choline supplement ranking. Citicoline is the other popular brain form; see our citicoline review.
The 5 best alpha-GPC supplements
Tap any product to jump straight to its full review.
Momentous Alpha GPC 300 mg (60 capsules)
Best for: Athletes and buyers who want a certified product
The only single-ingredient alpha-GPC we found with a confirmed contents certification, at a trial-range 300 mg. It costs the most, and its marketing overreaches.
- NSF Certified for Sport, which we confirmed on NSF's listing: the only single-ingredient alpha-GPC we found with a contents certification we could confirm
- 300 mg of alpha-GPC a day, inside the range used in healthy-adult trials
- Its current label on the brand's site names the ingredient, AlphaSize at 100 percent, with only cellulose, the capsule and two flow agents
- The highest daily cost of our picks, and the label does not state the choline (about 120 mg)
- Its listing markets growth hormone and endurance benefits that the small trials do not show, cites pro sports teams and suggests 300 to 600 mg a day though the directions say one capsule, and the bottle calls alpha-GPC highly bioavailable
- Only about 150 Amazon ratings, the fewest of our five picks
BulkSupplements Alpha GPC Powder (100 g)
Best for: The lowest daily cost
300 mg of alpha-GPC at the lowest daily cost here, with the carrier shown on the panel. You measure it yourself.
- The panel shows 300 mg of alpha-GPC from about 600 mg of powder, plus the calcium phosphate carrier, so the active amount is clear
- The lowest daily cost of any alpha-GPC we compared, and less in larger bags
- Only calcium phosphate and silica besides the alpha-GPC
- A quarter-teaspoon measure is approximate; a small scale gives a more even dose
- A gallery image headlines 600 mg per serving, which is the powder weight, not the alpha-GPC
- Its testing claim names no lab
Type Zero Clean Alpha GPC 600 mg (90 capsules)
Best for: Low-cost capsules at 600 mg
The lowest capsule cost per 300 mg, at 600 mg a day. Its listing misstates the per-capsule dose.
- The lowest capsule cost per 300 mg of alpha-GPC among our picks
- 600 mg a day, the top of the range used in healthy-adult trials, with directions that match on the label and listing
- Plain excipients: the capsule, stearic acid, magnesium stearate, silica and calcium silicate
- A listing bullet says 600 mg per capsule, but the label gives 600 mg per two capsules, and the listing's ingredient list differs from the label
- Calls its plant an "FDA approved facility"; the FDA registers supplement plants but does not approve them
- A smaller brand with about 250 ratings, no stated purity and an unnamed testing claim
Double Wood Alpha-GPC 300 mg (60 capsules)
Best for: Seeing the purity on the label
The clearest capsule label, printing the 50 percent purity. The public lot certificate is pass or fail only.
- One of only two capsules we found that print the 50 percent purity on the panel (the other, Deal Supplement, did not pass our seller check), so 600 mg of powder plainly means 300 mg of alpha-GPC
- Posts a lot certificate from an accredited lab, and is listed in ConsumerLab's Quality Certification Program, which brands pay to join
- About 5,300 ratings averaging 4.4 stars
- The public certificate reports only "Pass" against the 600 mg powder weight, not a measured alpha-GPC amount
- A mid-range daily cost for 300 mg, a little less in the 120-capsule size
- The listing's ingredient list names a gelatin capsule while the label lists a vegetarian one, and its copy calls alpha-GPC among the most bioavailable choline forms
NOW Foods Alpha GPC 300 mg (60 veg capsules)
Best for: Choosing 300 or 600 mg a day
A 300 mg capsule that lets you take 300 or 600 mg, sold by Amazon. Its label overstates absorption, and a listing bullet overstates the dose.
- One 300 mg capsule per serving, so you can take 300 or 600 mg a day
- Sold by Amazon, from a large brand that runs its own testing lab
- A mid-range daily cost at one capsule
- A listing bullet says 600 mg per serving, but the label serving is one 300 mg capsule
- The label says alpha-GPC is more bioavailable than other choline forms and that it enhances nerve cell communication, more than the trials show
- No independent contents certification; its quality claims describe its own labs and facility audits
The full lineup, side by side
Amounts come from each product's Supplement Facts panel on its Amazon listing, read November 3 and rechecked November 6, 2026; the Momentous purity line is from its current label on the brand's site. Choline is about 40.5 percent of alpha-GPC by weight; no label states it.
| Product | Alpha-GPC per day | Purity on label | Choline per day | Testing | Cost tier | Score |
|---|---|---|---|---|---|---|
| #1 Momentous | 300 mg | AlphaSize 100% (brand label) | About 120 mg | NSF Certified for Sport (confirmed) | $$$ | 4.1 |
| #2 BulkSupplements | 300 mg | Carrier shown | About 120 mg | Unnamed claim | $ | 4.0 |
| #3 Type Zero | 600 mg | Not stated | About 243 mg | Unnamed claim | $ | 3.8 |
| #4 Double Wood | 300 mg | 50% printed | About 120 mg | Lot certificate (pass only) | $$ | 3.7 |
| #5 NOW Foods | 300 to 600 mg | Not stated | About 120 to 243 mg | In-house, GMP audit | $$ | 3.7 |
Cost tiers compare the cost per day of the products on this page when we reviewed them ($ lower, $$ mid-range, $$$ higher). Prices change often, so check the current price on Amazon. Cost per day uses the label's lowest daily dose. Scores are rounded: Momentous scores 4.050 and BulkSupplements 3.975, and Double Wood (3.725) edges NOW (3.700).
How to choose, and what to check first
Find the active amount. If the panel says "Alpha GPC 50%," halve the number to get alpha-GPC. If it gives no purity, the number should be alpha-GPC itself, but you cannot tell from the label alone. Multiply by about 0.4 for the choline.
Keep to the studied range. Trials in healthy adults used 250 to 600 mg a day for up to two weeks; nothing we found tested months of use. For the full stroke and trial picture, see our alpha-GPC evidence review.
- Stroke and heart risk. If you are over 50 or have high blood pressure, heart disease, atrial fibrillation, diabetes, kidney disease, or a past stroke or mini-stroke, ask your doctor before taking alpha-GPC daily.
- Medicines. Ask your doctor first if you take dementia drugs such as donepezil, anticholinergic medicines (such as some bladder-control drugs) or Parkinson's medicines, and do not change those medicines on your own.
- Pregnancy, breastfeeding and children. We found no safety data; get choline from food or a prenatal vitamin instead.
Frequently asked questions
What is the best alpha-GPC supplement?
Momentous ranked first because it is the only single-ingredient alpha-GPC we found with a contents certification we could confirm, NSF Certified for Sport, at 300 mg a day. Among our picks, BulkSupplements powder and Type Zero capsules cost the least per 300 mg of alpha-GPC.
What does alpha-GPC 50% mean?
It means the powder is half alpha-GPC and half carrier, so 600 mg of a 50 percent powder supplies 300 mg of alpha-GPC. Some products headline the powder weight, so check the Supplement Facts panel.
Is 300 mg or 600 mg of alpha-GPC better?
We found no trial that compared 300 and 600 mg. The closest, a one-week trial in 48 college men, compared 250 and 500 mg a day: strength did not change at either dose, and jump power improved most at 250 mg, not 500 mg. Trials in healthy adults used 250 to 600 mg a day for up to two weeks, or single doses up to 1,000 mg; that range describes the research, not a proven benefit, and long-term use has not been tested.
Is alpha-GPC safe?
Its long-term safety has not been tested. Short trials reported few side effects, but they were too small and brief to detect rare problems. A study of 12 million Korean adults aged 50 and over linked prescription alpha-GPC with about 43 percent more strokes; it cannot show cause, but if you are over 50 or have heart or stroke risk factors, ask your doctor first.
How much choline is in alpha-GPC?
About 40.5 percent by weight, so 300 mg of alpha-GPC gives about 120 mg of choline and 600 mg about 243 mg. The Adequate Intake is 425 mg a day for women and 550 mg for men.
The bottom line
Alpha-GPC's benefits rest on small, short trials, and a large Korean records study raised a stroke question that is still open. If you still want to try it, choose 300 to 600 mg a day of a product whose label makes the active amount clear: Momentous is the only one with a certification we could confirm, and BulkSupplements and Type Zero cost the least of our picks. If you are over 50 or have heart or stroke risk factors, talk with your doctor first.