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If your blood has too little or too much vitamin B12, you might be at higher risk of dying from any cause or from heart disease — the safest range is in the middle, between 190 and 948 pg/mL.

59
Pro
48
Against

Evidence from Studies

Supporting (1)

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Community contributions welcome

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Associations of Serum Folate and Vitamin B12 Levels With Cardiovascular Disease Mortality Among Patients With Type 2 Diabetes

Cohort Study
Human
2022 Jan 4

This study found that people with type 2 diabetes who have either very low or very high levels of vitamin B12 are more likely to die from heart disease or other causes, which matches the claim that both too little and too much B12 can be harmful.

Contradicting (2)

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Community contributions welcome

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The origin of vitamin B12 levels and risk of all-cause, cardiovascular and cancer specific mortality: A systematic review and dose-response meta-analysis.

Systematic Review With Meta-Analysis
Human
2024 Feb

The study says having too much B12 is linked to higher death risk, but it doesn’t say having too little B12 is dangerous — so it doesn’t support the claim that both too much and too little are bad.

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Elevated Vitamin B12, Risk of Cancer, and Mortality: A Systematic Review

Systematic Review
Human
2024 Jul

This study only looked at what happens when vitamin B12 is too high, not when it’s too low, so it can’t tell us if both ends are dangerous like the claim says.

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Similar Assertions

For people with type 2 diabetes, having too little or too much vitamin B12 in the blood might increase the chance of dying from heart disease — the safest range seems to be in the middle.

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0
90%

People with vitamin B12 levels between 400 and 600 units in their blood are 34% more likely to die from any cause than people with lower levels—even though those levels are still considered normal by doctors.

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0
90%

In people with type 2 diabetes, having very high levels of vitamin B12 in the blood seems to be linked to a much higher chance of dying from heart disease—higher than at any other B12 level—so maybe high B12 isn’t helping, but instead signals something else wrong in the body.

59
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89%

People with very high levels of vitamin B12 in their blood—above 600 pmol/L—might be 50% more likely to die from any cause compared to those with lower levels, which could mean there’s a dangerous upper limit to how much B12 is safe.

48
0
88%

People with higher levels of vitamin B12 in their blood seem to have a higher chance of dying from heart problems, but this link isn’t as clear as the link between high vitamin B12 and dying from any cause.

48
0
86%

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