GlucoBerry review: maqui berry, chromium and biotin, checked against the evidence.

The short answer.

If a GlucoBerry ad about a blocked “Blood Sugar Drain” caught your eye, you are right to check before you pay. GlucoBerry is a capsule sold through ClickBank on bloodsugarberry.com. The page now carries the name MD/PROCESS in its title and header, the label says “MD Process” and “Doctor Formulated,” and the sales letter is signed “Dr. Mark S. Weis, MD.” We did not verify his credentials. The product is the same GlucoBerry, with four ingredients: maqui berry extract, gymnema leaf, chromium and biotin.

Our view, in one line: the maqui berry research is small and partly industry-funded, the “Blood Sugar Drain” story is not backed by any study the page names, and the biotin dose brings a real lab-test risk. Its refund terms are the most generous of the three products we reviewed: opened bottles do not have to be sent back. Before you buy any blood-sugar product, our free eight scam checks take about five minutes.

What the seller says.

These are the seller’s own words from the GlucoBerry order page on November 9, 2026. They are claims, not our findings.

• “Is Your Blood Sugar Drain Blocked?” The page says the kidneys have a “Blood Sugar Drain” and that “50% of Americans have too much of a sticky gray protein that clogs up their Blood Sugar Drain.” It credits “a study from Johns Hopkins University” and “Harvard research” without naming or linking either.
• “Taking Maqui Berry extract every day improved long-term blood sugar markers by 23%.”
• Chromium: “Twenty-six peer-reviewed studies” and “a Yale University study” on chromium with biotin, also not named.
• Gymnema: a study of 58 people, and “we took the same dose of Gymnema Leaf they used in the study.”
• “Adding Maqui Berry to your diet is just as healthy as adding more blueberries to your diet.”

We could not match the 23% figure to the maqui studies we found: in the three-month study of the same 180 mg daily amount, A1C went from 5.65% to 5.35% (see below). The two small placebo-controlled gymnema trials we found used 600 mg a day, more than the 400 mg in GlucoBerry. And an extract in a capsule is not the same thing as eating berries.

The page also offers a “30-day supply” at $59, but the order buttons we saw start at two bottles.

What is in each capsule.

Amounts from the sample label on bloodsugarberry.com, read November 9, 2026. Evidence summaries from the sources listed at the end of this page.

What the evidence says overall.

1. GlucoBerry itself has not been studied. A PubMed search on November 9, 2026 returned no published trial of the product.
2. The maqui berry evidence is early. In a crossover study of 10 people with glucose intolerance, the extract taken before a rice meal reduced the rise in glucose and insulin after that one meal. In the three-month study of 31 people with newly found glucose intolerance taking 180 mg each morning, A1C went from 5.65% to 5.35%, fasting glucose did not change significantly, and the abstract describes no placebo group. A 2026 systematic review found consistent one-meal effects but modest and inconsistent long-term results; two of its authors work for a berry company.
3. Chromium and gymnema are weak and mixed. NCCIH says chromium has only weak evidence of a possible benefit for diabetes, from studies too varied to draw clear conclusions. The American Diabetes Association, as cited by NIH, found the evidence insufficient for routine chromium use.

The “Blood Sugar Drain” is the page’s own name, and the page names no study showing that maqui berry clears a “sticky gray protein” from the kidneys. The FDA does not approve dietary supplements before they are sold.

Medicines, lab tests and who should not take it.

• Diabetes medicines. NIH warns that chromium may add to the effect of insulin, metformin and other diabetes medicines and raise the risk of low blood sugar.
• Lab tests. The FDA has warned that biotin can interfere with lab tests and has received reports of falsely low troponin results, a test used to diagnose heart attacks; NIH reports one death after such a result. NIH also notes a single 10 mg dose has distorted thyroid tests. Tell your doctor and the lab about GlucoBerry before any blood test.
• Thyroid medicine. A small study found chromium picolinate reduced the absorption of levothyroxine, a thyroid hormone medicine. Ask your prescriber how to time them.
• Kidneys and liver. NIH lists rare case reports of kidney and liver problems with high chromium intakes, and says people with kidney or liver disease may be more sensitive. Gymnema has rare reports of liver injury.
• Stacking products. Taking GlucoBerry with Gluco6, which has 1,000 mcg of chromium, would add up to 1,600 mcg of chromium a day.
• Pregnancy and breastfeeding. The page tells anyone pregnant, nursing, taking medication or with a medical condition to consult a physician first.

Price, shipping and refunds (read November 9, 2026).

Shipping outside the US is $19.95 on 2 or 3 bottles. The seller says each order is a one-time payment with no subscription.

Refunds. The order page offers a 180-day “Empty Bottle” refund from the date of purchase and says it will refund you “even if you’ve used up your whole supply.” The refund policy page (dated November 16, 2022) adds the details: contact MD/PROCESS within 180 days of the order date (not the delivery date) with your name, email and order number; send back only unopened bottles, at your own shipping cost; opened or empty bottles do not need to be returned. It says refunds take up to 5 to 7 business days.

Run the scam checks on this page yourself.

Our article on supplement scams walks through eight checks you can run on any blood-sugar product in about five minutes. Here is how the GlucoBerry page looks on some of those checks and warning signs.

A missing answer is not proof of fraud. It is a reason to slow down and ask your care team.

Want to check a claim step by step? Use the free Source Credibility Checklist on screen.

Questions to take to your doctor or pharmacist.

• Could 600 mcg of chromium a day interact with any medicine I take?
• Should I stop biotin before my next blood test, and for how long?
• Do any of my other supplements also contain chromium or biotin?
• Would this change how I should check my blood sugar?

Bring the label, or this page. The free Care-Team Conversation Planner helps you write the questions down and record the answer.

If you decide not to buy, here is a five-minute next step.

Choosing not to buy is a reasonable decision, not a missed chance. If you still want to do something today, try this:

GlucoBerry questions, answered.

The bottom line.

GlucoBerry is simpler than most blood-sugar blends: four ingredients with their amounts shown, and a long refund window. The evidence behind it is still thin. The maqui berry studies are small, short and partly funded by the extract’s supplier; chromium and gymnema have weak and mixed results; and the biotin dose can distort lab tests. The product has no published trial of its own. If you are curious, start with a conversation with your care team.