Does vitamin B12 raise blood pressure?

Not at the doses in food or ordinary supplements, as far as any trial has looked, and no trial has tested B12 on its own. In a 5-year randomized trial of 2,501 people with past heart disease, a B-vitamin pill with 20 mcg of B12 a day, given together with folate and B6, did not change blood pressure. The one documented rise comes from a very different product. When healthy volunteers were given 5 g of hydroxocobalamin, a form of B12 used as a cyanide antidote, into a vein, about 18% reached 180 systolic or 110 diastolic or higher, according to the FDA label.

Established. Vitamin B12 has no tolerable upper intake level. The NIH Office of Dietary Supplements says none was set because of its low potential for toxicity. The antidote dose is given intravenously and is a pharmacological dose, not a nutritional one.

Unsettled. Whether B12 alone moves blood pressure in either direction is untested. The trials that measured blood pressure gave B12 together with folate and B6, and the population surveys disagree with each other.

Ratios from B12 research: stroke in trials, hypertension in surveys

Randomized trialsObservational data

Trial rows are risk ratios, survey rows are odds ratios from cross-sectional data, which cannot show cause. The two surveys point in opposite directions. In the Cochrane review stroke occurred in 4.3% of people on B vitamins against 5.1% on placebo. Sources: cards ev-b12bp-01, ev-b12bp-02, ev-b12bp-06 and ev-b12bp-07 below.

What the trials found

The SU.FOL.OM3 trial randomized 2,501 people with a history of cardiovascular disease to B vitamins (560 mcg of 5-methyl-THF, 3 mg of B6 and 20 mcg of B12), omega-3 fats, both or placebo, for a median of 4.7 years. Neither supplement changed blood pressure in crude or adjusted models. The B12 dose was close to what a diet can supply, and its effect cannot be separated from the folate given alongside it.

Most B12 trials were built to lower homocysteine and test whether that cut heart disease, with blood pressure in the background. A Cochrane review of 15 randomized trials in 71,422 people found B vitamins cut stroke slightly, 4.3% against 5.1% on placebo (RR 0.90, 95% CI 0.82 to 0.99), and did not change heart attacks (RR 1.02). A meta-analysis of 14 trials in 54,913 people found stroke down by 7% (RR 0.93, 95% CI 0.86 to 1.00). Its authors looked at B12 dose and baseline B12 level and found no significant benefit for either.

The closest blood-pressure meta-analysis concerns folic acid, which is usually sold and trialled with B12. Across 22 trials in 41,633 people, folic acid lowered systolic pressure by 1.10 mm Hg (WMD -1.10, 95% CI -1.93 to -0.28) and diastolic by 0.24 mm Hg. We found no comparable analysis for B12 alone.

Unsettled. One network meta-analysis covering 150 patients with chronic heart failure reported that B6, folic acid and B12 taken together slightly raised systolic and diastolic pressure. The abstract gives no size for the change and mixes the language of trials with single-group studies, and we could not get the full text to check its design. It is the only source here that points to a rise from oral B vitamins, and it is too thin to carry that claim.

The population surveys disagree

In 55,569 US adults from the NHANES survey, people in the top quarter of dietary B12 intake had lower odds of hypertension than those in the bottom quarter, an odds ratio of 0.84 in men and 0.87 in women. A smaller NHANES analysis of 3,654 adults, which counted supplements as well as food, found the opposite, with an odds ratio of 1.39. Both are snapshots at one point in time. People who already have high blood pressure may take more supplements, and people who eat more B12 tend to eat differently overall, so neither survey can show what B12 does.

Who should be careful

Not for everyone. Intravenous hydroxocobalamin raises blood pressure, and this is a known effect of the drug. The FDA label for Cyanokit reports blood pressure at or above 180 systolic or 110 diastolic in approximately 18% of healthy subjects given 5 g and 28% given 10 g. It is a hospital antidote for cyanide poisoning, and the label does not apply to food or oral supplements.

Intensive care units have tested the same effect on purpose. In a pilot randomized trial of 20 adults in septic shock, a single 5 g intravenous dose of hydroxocobalamin cut the dose of blood-pressure drugs needed by 36%, against a 4% rise on placebo. That is a pharmacological dose given into a vein, far beyond nutrition, in a small feasibility trial.

Pregnancy is the gap that matters most here. Pooled observational studies found women with preeclampsia had serum B12 lower by 15.24 pg/mL than women with normal blood pressure in pregnancy, with very high heterogeneity between studies, so low B12 may be a marker and not a cause. A systematic review found no intervention trial at all of B12 supplements before or during pregnancy. The interactions list we searched for B12 named no medicine that changes blood pressure with it. We found no card on children or on kidney disease, and that silence is a gap in the evidence. It is not a finding of safety.

What expert bodies say

The NIH Office of Dietary Supplements states that B12 and folic acid supplements lower homocysteine levels but not cardiovascular disease risk, and that no upper limit was set for B12 because of its low potential for toxicity. The FDA prescribing information for intravenous hydroxocobalamin lists raised blood pressure under warnings and precautions. We found no agency that has taken a position on oral B12 and blood pressure specifically.

How we searched

Searched: a local copy of PubMed, on 7 October 2026. The broadest query paired B12 and its forms, B vitamins or homocysteine with blood pressure, hypertension, systolic pressure or preeclampsia (753 hits). A second paired hydroxocobalamin and B12 with blood pressure, hypotension or vasoplegia (373 hits). Narrower queries covered folate and B-vitamin meta-analyses on blood pressure (37), B vitamins with omega-3 (2) and the Cochrane homocysteine review (5 hits, the latest of 4 versions used).

Also searched: the web for a meta-analysis of B12 alone and blood pressure (none found) and for recent NHANES analyses. We read the FDA label through DailyMed and the openFDA label service. We also checked the NIH Office of Dietary Supplements fact sheet, an interactions table (7 rows for B12, none about blood pressure), ClinicalTrials.gov (no registered trial of B12 and blood pressure) and Retraction Watch for every cited paper (none retracted).

Included: three meta-analyses of randomized trials, a network meta-analysis in heart failure whose design we could not check, one large randomized trial and a pilot trial in septic shock. Also two survey analyses, a meta-analysis of observational pregnancy studies, a systematic review of vitamin trials in pregnancy, the Cyanokit label and two NIH statements. Thirteen cards in total: 4 at level A, 2 at B, 4 at C and 3 at E.

Excluded: a trial on arterial stiffness whose abstract gives no blood-pressure result, a Cochrane review in diabetic kidney disease that reports renal outcomes only, and an umbrella review that does not report B12 separately. Case reports and reviews on vasoplegia already covered by the septic shock trial and the label were dropped too. Two 2026 methylcobalamin trials without blood-pressure outcomes were also left out.

What we read: abstracts for the studies, each quotation checked against the abstract text. The warnings section of the Cyanokit label, confirmed in two independent sources, and the NIH fact sheet sections on heart disease, upper limits and interactions.

What we could not get: the full text of the Cochrane review, which refused our request, and the full text of the heart failure network meta-analysis, so its design could not be checked.

What would change this answer

A randomized trial of B12 alone, at food or common supplement doses, with blood pressure as the main outcome. We found none published and none registered.
A trial of B12 supplements before or during pregnancy that measures blood pressure and preeclampsia, which the observational link would justify.
The full design and effect sizes of the heart failure analysis, which would show whether its reported rise holds up.

The rest of the nutrient, in one place. Vitamin B12: who actually needs to worry, and why the damage can be permanent → What it does, how much you need, who runs short, and what too much does, with the evidence level shown on every line.

The full guide

Vitamin B12: who actually needs to worry, and why the damage can be permanent

The same question for other foods (blood pressure)

Sources

ev-b12bp-01 · Meta-analysis or systematic review · Cochrane systematic review and meta-analysis of RCTs · n = 71,422
Compared with placebo, homocysteine-lowering interventions were associated with reduced stroke outcome (homocysteine-lowering = 4.3% versus comparator = 5.1%, RR 0.90, 95% CI 0.82 to 0.99, I2 = 8%, 10 trials, N = 44,224; high-quality evidence).
Who: people with and without cardiovascular disease given vitamin B6, B9 or B12 to lower homocysteine, follow-up 1 to 7.3 years
Effect: stroke RR 0.90 (95% CI 0.82 to 0.99, 10 trials, N 44,224); myocardial infarction RR 1.02 (0.95 to 1.10); all-cause death RR 1.01
Certainty: high-quality evidence by GRADE; B12 mostly given with folic acid, effect of B12 alone not isolated
Cochrane Database Syst Rev, 2017 · checked 2026-10-07 · we read the abstract
ev-b12bp-02 · Meta-analysis or systematic review · meta-analysis of randomized controlled trials · n = 54,913
We conducted detailed subgroup analyses for cyanocobalamin (vitamin B12) but did not find a significant benefit regarding intervention dose of vitamin B12 or baseline blood B12 concentration.
Who: participants of 14 randomized trials of B vitamin supplementation for homocysteine lowering
Effect: stroke RR 0.93 (95% CI 0.86 to 1.00); no significant benefit by vitamin B12 dose or baseline B12
Certainty: blood pressure is a subgroup modifier here, not an outcome; fixed-effects model
Neurology, 2013 · checked 2026-10-07 · we read the abstract
ev-b12bp-03 · Randomized controlled trial(s) · double-blind randomized placebo-controlled factorial trial · n = 2,501
No effect of supplementation with either n-3 PUFA or B-vitamins on BP was observed in crude and adjusted multivariate models.
Who: patients with a history of cardiovascular disease in the SU.FOL.OM3 trial, 2 x 2 factorial; B vitamins were 5-methyl-THF 560 ug, B6 3 mg, B12 20 ug
Effect: no effect of B vitamins on blood pressure in crude or adjusted models; median 4.7 years
Certainty: B12 given only with folate and B6; dietary dose, not high dose
Br J Nutr, 2012 · checked 2026-10-07 · we read the abstract
ev-b12bp-04 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 41,633
The pooled results of 22 studies, including 41,633 participants, showed that folic acid supplementation significantly decreased systolic BP (SBP) (WMD: -1.10 mmHg; 95% CI: -1.93 to -0.28; p = 0.008).
Who: participants in randomized trials of folic acid supplementation
Effect: systolic BP WMD -1.10 mmHg (95% CI -1.93 to -0.28); diastolic -0.24 mmHg (-0.37 to -0.10)
Certainty: about folic acid; included because B12 is usually sold and trialled with it; no comparable B12-alone meta-analysis found
Crit Rev Food Sci Nutr, 2023 · checked 2026-10-07 · we read the abstract
ev-b12bp-05 · Observational data · network meta-analysis of randomized controlled trials · n = 150
Clinical trials among patients diagnosed with chronic heart failure showed that the intake of synthetic forms of pyridoxine, folic acid, and cyanocobalamin slightly increases systolic, diastolic and central venous pressure while decreasing the heart rate and increasing LVEF.
Who: patients with chronic heart failure with reduced ejection fraction
Effect: slight increase in systolic, diastolic and central venous pressure; no size reported in the abstract
Certainty: very low: abstract mixes trial and single-group language, gives no effect sizes; no PMC full text
Cardiovasc Hematol Disord Drug Targets, 2023 · checked 2026-10-07 · we read the abstract
ev-b12bp-06 · Observational data · cross-sectional analysis of a national survey · n = 55,569
Among male participants, dietary folate, vitamin B6, and vitamin B12 intakes were significantly and negatively associated with the prevalence of hypertension, with multivariate-adjusted odds ratios (ORs) of 0.61 (95% confidence interval [CI], 0.55-0.68), 0.65 (95% CI, 0.59-0.72), and 0.84 (95% CI, 0.75-0.95) for the highest quartile group compared with the lowest group.
Who: US adults, NHANES III and 1999 to 2014, 24-hour dietary recalls
Effect: hypertension OR highest vs lowest B12 quartile: men 0.84 (95% CI 0.75 to 0.95), women 0.87 (0.77 to 0.98)
Certainty: cross-sectional; dietary B12 tracks with overall diet; cannot show cause
Nutr Res, 2023 · checked 2026-10-07 · we read the abstract
ev-b12bp-07 · Observational data · cross-sectional analysis of a national survey · n = 3,654
Vitamin B12 shown positive associations with hypertension in the total population, 20-39 years old and ≥60 years old OR (95%CI) =1.39 (1.13, 1.71), 1.82 (1.23, 2.69), and 1.63 (1.04, 2.54), respectively.
Who: US adults aged 20 and over, NHANES, two 24-hour recalls plus supplement survey
Effect: hypertension OR 1.39 (95% CI 1.13 to 1.71) overall; 1.82 at 20 to 39 years; 1.63 at 60 and over; B12 inversely linked to diastolic pressure at 60 and over
Certainty: cross-sectional; reverse causation likely (people with hypertension use more B12-containing supplements)
PLoS One, 2025 · checked 2026-10-07 · we read the abstract
ev-b12bp-08 · Observational data · systematic review and meta-analysis of observational studies · n = —
Vitamin B12 levels in women with preeclampsia were significantly lower than those in healthy women (mean, -15.24 pg/mL; 95%CI, -27.52 to -2.954; P < 0.015), but heterogeneity between studies was high (I2 = 97.8%; P = 0.0103).
Who: pregnant women with preeclampsia vs normotensive pregnant women in observational studies
Effect: mean difference -15.24 pg/mL (95% CI -27.52 to -2.954); I2 97.8%
Certainty: very high heterogeneity; low B12 may be a marker, not a cause
Nutr Rev, 2021 · checked 2026-10-07 · we read the abstract
ev-b12bp-09 · Meta-analysis or systematic review · systematic review and meta-analysis of controlled trials · n = —
Despite the prevalence of vitamin B12 deficiency amongst populations with limited intake of animal source foods, no intervention trials have evaluated vitamin B12 supplementation before or during pregnancy.
Who: pregnant women in controlled trials of vitamins B6, B12 or C
Effect: no B12 supplementation trial in pregnancy identified
Certainty: search to about 2011; a gap statement, not an effect
Paediatr Perinat Epidemiol, 2012 · checked 2026-10-07 · we read the abstract
ev-b12bp-10 · Randomized controlled trial(s) · phase 2 double-blind placebo-controlled pilot RCT · n = 20
In the high-dose IV hydroxocobalamin group, compared to placebo, there was a greater reduction in vasopressor dose between randomization and postinfusion (-36% vs 4%, P < .001) and randomization and 3-h postinfusion (-28% vs 10%, P = .019).
Who: critically ill adults with septic shock (Sepsis 3), single 5 g IV hydroxocobalamin vs saline
Effect: vasopressor dose change -36% vs +4% after infusion (P < .001); -28% vs +10% at 3 hours (P = .019)
Certainty: pharmacological IV dose, not a nutritional one; small feasibility trial
Chest, 2023 · checked 2026-10-07 · we read the abstract
ev-b12bp-11 · Position of an expert body · FDA-approved prescribing information, Warnings and Precautions 5.4 · n = 84
Elevations in blood pressure (≥180 mmHg systolic or ≥110 mmHg diastolic) were observed in approximately 18% of healthy subjects (not exposed to cyanide) receiving hydroxocobalamin 5 g and 28% of subjects receiving 10 g.
Who: healthy subjects not exposed to cyanide given IV hydroxocobalamin 5 g or 10 g
Effect: BP at or above 180 systolic or 110 diastolic in about 18% (5 g) and 28% (10 g); transient, maximal near end of infusion
Certainty: applies to the antidote dose given intravenously, not to food or oral supplements
CYANOKIT (hydroxocobalamin) prescribing information, BTG International, DailyMed setid d56fcc8d-bd64-46ab-b0c0-2124bd745a6b, 2023 · checked 2026-10-07 · we read the section
ev-b12bp-12 · Position of an expert body · agency fact sheet · n = —
The FNB did not establish a UL for vitamin B12 because of its low potential for toxicity [1].
Who: general population, NIH Office of Dietary Supplements vitamin B12 fact sheet
Effect: no UL set by the Food and Nutrition Board
Certainty: concerns oral intake; IV antidote doses are a separate case (ev-b12bp-11)
NIH Office of Dietary Supplements, Vitamin B12 fact sheet for health professionals · checked 2026-10-07 · we read the section
ev-b12bp-13 · Position of an expert body · agency fact sheet · n = —
RCTs have found that vitamin B12 (and folic acid) supplements lower homocysteine levels but not CVD risk.
Who: general population, NIH Office of Dietary Supplements vitamin B12 fact sheet
Effect: homocysteine lowered, cardiovascular risk unchanged
Certainty: summary of RCTs and the Cochrane review (ev-b12bp-01)
NIH Office of Dietary Supplements, Vitamin B12 fact sheet for health professionals · checked 2026-10-07 · we read the section

How this page was made. Evidence was extracted from primary sources into cards, every number was re-checked against the source, and the text was written from those cards. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.