Factors that increase serum homocysteine levels

Physiological factors (“physiological”: also know as “this is not a disease”)

  • Higher age
  • Being male
  • Menopause in women
  • High muscle mass

Dietary factors

  • Low intake of folate (folic acid)
  • Low intake of vitamin B12
  • Low intake of vitamin B6
  • Drinking coffee [This does not mean that drinking coffee is unhealthy.]
  • Drinking alcohol [This does not mean that drinking alcohol in moderate amounts is unhealthy - although it may be.]
  • Very high intake of the amino acid methionine [Ward et al. 2001]
  • Low intake of omega-3 fatty acids (?)

Diseases or deficiencies

  • Folate, vitamin B12, or vitamin B6 deficiency (Vitamin B12 deficiency is the one that is most relevant for vegans and vegetarians. A deficiency in folate or vitamin B6 does not usually occur in vegans. Vegans typically have a high intake of folate.)
  • Renal impairment (i.e., impaired kidney function; kidney disease)
  • Iodine deficiency (?) - high thyroid-stimulating hormone (TSH) levels are positively associated with plasma total homocysteine (tHcy) [Hvas & Nexo 2005: (r = 0.45; p = 0.02)]
  • Hypothyroidism (which can be caused by iodine deficiency or iodine and selenium deficiency)
  • Diabetes
  • Psoriasis (an inflammatory skin disease)
  • Malignancies (cancer)

Other lifestyle factors

  • Smoking cigarettes
  • Lack of physical activity


  • Lipid-lowering medications  (namely: cholestyramine, nicotinic acid, fibric acid derivatives [e.g., fenofibrate]; NOT statins; “lipid-lowering” means cholesterol-lowering drugs)
  • Anticonvulsants (namely: phenytoin or carbamazepine; “anticonvulsants” are medications to control seizures.)
  • Sex hormones (androgens; this means “testosterone supplements” also known as “steroid”, “anabolics”, or “anabolic steroids”, the ones that some bodybuilders use.)
  • Antirheumatic drugs (namely: methotrexate)
  • Some other medications (namely: ciclosporin, diuretics, levodopa, methionine loading medications [oral, intravenous, peritoneal], theophylline, trimethoprim)

Genetic factors (i.e. genetic predisposition; these are all problems with the functioning of some enzyme.)

  • Homozygosity for 5,10-Methylenetetrahydrofolate reductase C677T polymorphism (which causes decreased activity of this enzyme; this one is common.)
  • Cystathionine gamma-lyase deficiency (This one is common.)
  • Heterozygosity for cystathionine β synthase (CBS) deficiency (This one is uncommon.)
  • Homocystinuria (caused by homozygous CBS deficiency) (This one is very rare.)

Based on:

Hankey, GJ: B vitamins for stroke prevention; Stroke Vasc Neurol; 2018 Jun 6;3(2):51-58. doi: 10.1136/svn-2018-000156; eCollection; https://pubmed.ncbi.nlm.nih.gov/30022794/

Homocysteine (often abbreviated as "Hcy"):

Homocysteine is basically like the amino acid cysteine with an extra carbon atom (C), see cysteine below (the "chain" is one "corner" [= carbon atom] shorter):