Homocysteine

Normally, your homocysteine levels are low. That's because your body uses vitamin B12, vitamin B6, and folic acid (also called folate or vitamin B9) to quickly break down homocysteine and change it into other substances that your body needs. High levels of homocysteine in your blood may be a sign that this process isn't working right or that you're lacking certain B vitamins. Because of this link, homocysteine is sometimes checked alongside another marker called methylmalonic acid (MMA) to help diagnose vitamin B12 or folate deficiency, especially when red blood cells appear larger than usual on a blood count.

If homocysteine isn't broken down, it can build up in your blood and may damage the lining of your arteries (the blood vessels that carry oxygen-rich blood from your heart to the rest of your body). Higher homocysteine levels are linked to higher rates of heart and blood vessel disease in some studies, but large clinical trials have shown that lowering homocysteine with B-vitamin supplements does not reduce heart attacks, strokes, or deaths. Because of this, current heart disease guidelines do not recommend routine homocysteine testing to estimate cardiovascular risk in most people.

Higher than normal homocysteine levels may happen with conditions such as osteoporosis, chronic kidney disease, hypothyroidism, schizophrenia, or Alzheimer's disease or other types of dementia.

If your homocysteine levels are high, it doesn't always mean you have a medical condition that needs treatment. If you have questions about your results, talk with your provider.