B12 is not a general glucose-control prescription
NIH describes B12’s roles in blood and nerve health. That does not supply a regimen for lowering blood glucose. NCCIH cautions against replacing effective diabetes care with unproven supplements, including products marketed as natural alternatives to medicine. [1][2]
Metformin can reduce B12 status
MHRA advises that B12 deficiency is a common metformin adverse effect, with greater risk at higher doses, longer duration and in people with other risk factors. It recommends testing when deficiency is suspected and considering periodic monitoring in those at risk. [3]
Nerve symptoms can have more than one explanation
Tingling, tiredness or other symptoms in a person with diabetes should not automatically be assigned to high glucose alone. MHRA notes that B12 deficiency and diabetes-related or unrelated problems can overlap. Appropriate assessment helps choose the right treatment. [3]
Correction does not usually require stopping metformin
MHRA explicitly advises that metformin can continue while B12 is corrected when it remains tolerated and is not contraindicated. Do not independently stop diabetes medicine or use improvement in energy as proof that glucose control is adequate. [3]
Review unexpected readings in context
Imagine glucose readings change after a new B12-containing drink is started. Check the full product, food intake, medicines and monitoring pattern. The vitamin name alone does not establish the cause; follow the diabetes care plan for concerning readings. [4][2]
| Question | Relevant response |
|---|---|
| Low B12 on metformin | Assess and correct as appropriate |
| Glucose control | Continue the diabetes treatment plan |
| New nerve symptoms | Consider multiple possible causes |
| New blended product | Review the complete formula |
Sources for this article
- Vitamin B12 - Health Professional Fact Sheet
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product. - Diabetes and Dietary Supplements: What You Need To Know | NCCIH
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product. - Metformin and reduced vitamin B12 levels: new advice for monitoring patients at risk - GOV.UK
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product. - Dietary Supplements: What You Need to Know
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product.