Sublingual vitamin B12 supplements are generally well-tolerated and are available in the form of tablets or lozenges that dissolve under the tongue. There is no significant evidence that suggests sublingual B12 differs in absorption efficacy from other forms¹².

Although vitamin B12 supplements are considered safe at high doses, they might cause side effects in some individuals. Reports of gastrointestinal issues, including upset stomach, nausea, and diarrhea, are relatively rare but possible³.

If you're experiencing stomach issues with sublingual B12 supplements, it's important to consider:

1. Dosage: High doses may contribute to gastrointestinal discomfort. Consider reducing the dose.
2. Other Ingredients: Some sublingual supplements contain sweeteners, flavorings, or other ingredients which might irritate the stomach.
3. Underlying Conditions: If you have gastrointestinal conditions such as IBS or GERD, these could be exacerbated by the supplement.

If the stomach issues persist, it may be advisable to consult a healthcare professional to rule out other potential causes and to discuss whether a different form of vitamin B12 or dosage adjustment might be appropriate for you.

Footnotes

1. Office of Dietary Supplements - Vitamin B12 ↩

2. Office of Dietary Supplements - Vitamin B12 Consumer ↩

3. Nutrition Source - Vitamin B12 ↩