Homocysteine
Reads: Homocysteine
The same Molecule Feeds Methylation or Antioxidant Defense, and b-vitamin Status Decides Which. Remethylation needs folate and B12; transsulfuration needs B6. That is why a single deficiency can present as either an epigenetic or a redox problem. Raised homocysteine is a marker of the fork being blocked, not a toxin in its own right — lowering it with vitamins has repeatedly failed to reproduce the outcome benefit its epidemiology predicted.
What this marker reads
The junction metabolite — remethylated back to methionine, or committed down transsulfuration to cysteine.
What a named body publishes
Each line below is the sentence the issuing body wrote, carried with its own identifier. Nothing here interprets your result — it states what was published, for whom, and by whom.
Homocysteine
“For adults aged 15-65 years in a folate-supplemented or folate-fortified population, the upper reference limit for fasting total homocysteine is 12 umol/L.” 15-65
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“For adults aged 15-65 years in a non-supplemented, non-fortified population, the upper reference limit for fasting total homocysteine is 15 umol/L.” 15-65
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“For people aged 65 years and over in a folate-supplemented or folate-fortified population, the upper reference limit for fasting total homocysteine is 16 umol/L.” 65 and over
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“For people aged 65 years and over in a non-supplemented, non-fortified population, the upper reference limit for fasting total homocysteine is 20 umol/L.” 65 and over
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“For children under 15 years in a folate-supplemented or folate-fortified population, the upper reference limit for fasting total homocysteine is 8 umol/L.” under 15
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“For children under 15 years in a non-supplemented, non-fortified population, the upper reference limit for fasting total homocysteine is 10 umol/L.” under 15
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“In pregnancy in a folate-supplemented or folate-fortified population, the upper reference limit for fasting total homocysteine is 8 umol/L.” females, pregnancy
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
“In pregnancy in a non-supplemented, non-fortified population, the upper reference limit for fasting total homocysteine is 10 umol/L.” females, pregnancy
Facts and Recommendations about Total Homocysteine Determinations: An Expert Opinion · Clinical Chemistry · 2004 DOI 10.1373/clinchem.2003.021634
Your laboratory reads your result against its own assay, and this page does not do that for it. What is above is what a named body published and for whom; what is below is the machinery the marker reads and the formulas witnessed on it.
What moves it
One-carbon metabolism lowers it.
Remethylation consumes homocysteine and returns it to methionine. Carried by the intermediary-metabolism and clinical reviews. doi 10.1016/j.molmet.2023.101755 · PMC9967593
Betaine methyl donor lowers it.
A second, independent route out of the fork - remethylation without folate or B12, which is why choline status can partly compensate for folate status and vice versa. Carried by the intermediary-metabolism, micronutrient and clinical reviews (PMC9967593; doi 10.3390/nu18132141; PMC12673670; doi 10.1016/j.molmet.2023.101755). Verbatim: “The pooled estimate of effect for betaine supplementation on plasma homocysteine was a reduction of 1.23 μmol/L, which was statistically significant (95% confidence interval, - 1.61 to - 0.85; P =.01)”. doi 10.3390/nu18132141 · PMID 23997720 · PMC9967593
NAD methylation leak raises it.
SAM consumption yields S-adenosylhomocysteine, which is hydrolyzed to homocysteine. doi 10.3389/fphar.2024.1410479
What it moves
It raises Sulfur clearance route.
The alternative fate - committed to cystathionine and then cysteine. Carried by the intermediary-metabolism and clinical reviews. doi 10.1016/j.molmet.2023.101755 · PMC9967593
It lowers Heart & blood pressure.
A marker of the fork being blocked, not a toxin in its own right - vitamin lowering of homocysteine has repeatedly failed to reproduce the outcome benefit its epidemiology predicted. Carried by the intermediary-metabolism and clinical reviews. doi 10.1016/j.molmet.2023.101755 · PMC9967593
It lowers Memory & focus.
Same caveat - strong association, weak intervention record. Carried by the intermediary-metabolism and clinical reviews. doi 10.1016/j.molmet.2023.101755 · PMC9967593
Formulas that modulate it
Each formula page names this pathway and carries the study behind its claim.
Build a combo from your panel
Open the bloodwork builder and select every marker your lab flagged — it covers the most machinery with the fewest formulas.