Magnesium vs Berberine
for blood sugar
Stronger evidence: Berberine
Stronger effect: Berberine
Safety: Berberine has the more serious interaction profile (minor vs moderate).
For blood sugar, Berberine has the stronger evidence grade.
Magnesium
grade C moderate certainty
modest improvement in insulin sensitivity / fasting glucose, mainly in deficiency or diabetes
250–400 mg/day, adults with insulin resistance
Berberine
grade B moderate certainty
lowers fasting glucose and HbA1c; GI side effects common
500 mg ×3/day, adults with elevated glucose
sources: PMID:42197052 · PMID:00000030