The research behind our ingredients

In 29-week metformin clinical trials, previously normal serum B12 levels fell to subnormal levels in approximately 7% of patients, according to the FDA-approved prescribing information, which advises measuring B12 at 2- to 3-year intervals.

In a 2016 analysis of the Diabetes Prevention Program Outcomes Study, low or borderline-low B12 was found in 20.3% of long-term metformin users vs 15.6% on placebo at 13 years, and each year of metformin use was associated with a 13% higher odds of B12 deficiency.

In June 2022, the UK medicines regulator classified reduced vitamin B12 as a common side effect of metformin, which may affect up to 1 in 10 people taking it, and advised periodic B12 monitoring in people with risk factors.

The American Diabetes Association's 2026 Standards of Care recommend considering periodic assessment of vitamin B12 levels in people receiving long-term metformin therapy (Recommendation 3.10), with annual monitoring for those on metformin for more than 4 years.

A meta-analysis of 17 studies found a pooled B12 deficiency rate of 23.2% in people taking metformin vs 17.4% in those not taking it, with longer duration and higher doses linked to greater risk.

A 1971 BMJ study found reduced B12 absorption in 21 of 71 (30%) patients with diabetes on long-term metformin, and the authors advised an annual B12 test for everyone on long-term metformin.

In a records analysis of 4,281 adults with low B12, sublingual B12 tablets raised serum B12 levels at least as much as intramuscular injections (mean rise 252 vs 218 ng/L).

In a randomized trial of 30 adults with low B12, 500 µg of B12 taken sublingually or orally for 4 weeks raised serum levels from about 100 to about 290 pmol/L, with no difference between the two routes.

A Cochrane review found low-quality evidence that high-dose oral B12 and intramuscular B12 have similar effects on normalizing serum B12 levels; one included trial used 2,000 µg/day orally.

In March 2024, NOW Foods lab-tested 12 creatine gummy brands. About half did not meet the creatine amount stated on their label.

A 2025 GRADE-assessed meta-analysis pooled 82 randomized controlled trials of Nigella sativa involving 5,026 participants, at doses of 200 to 4,600 mg/day for 1 to 48 weeks.

An umbrella review of 7 meta-analyses found that Nigella sativa supplementation increased total antioxidant capacity and superoxide dismutase (SOD) activity and lowered malondialdehyde, a marker of oxidative stress.

Reviews identify thymoquinone, the main component of the seed's essential oil, as responsible for much of black seed's biological activity, including its antioxidant properties.

As of October 2026, ClinicalTrials.gov lists 65 registered clinical studies with Nigella sativa as an intervention.