Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- What is homocysteine?
- Why is it important to monitor homocysteine levels?
- What are the possible symptoms or features of elevated homocysteine levels?
- What is considered a high level for homocysteine?
- What causes elevated homocysteine levels?
- Can elevated homocysteine levels be genetic?
- Can nutritional problems cause elevated homocysteine levels?
- How common is hyperhomocysteinemia?
- How can homocysteine levels be lowered?
- How many vitamins should I take to lower my homocysteine level?
- Does lowering homocysteine levels prevent heart attacks and strokes?
- What should I do to prevent heart attacks and strokes?
- Who should undergo testing for homocysteine blood levels?
What is considered a high level for homocysteine?
Homocysteine levels are measured in the blood by taking a blood sample. Normal levels are in the range between 5 to 15 micromoles (measurement unit of small amount of a molecule) per liter. Elevated levels are classified as follows:
- 15-30 micromoles per liter as moderate
- 30-100 micromoles per liter as intermediate
- Greater than 100 micromoles per liter as severe
What causes elevated homocysteine levels?
Homocysteine is chemically transformed into methionine and cysteine (similar amino acids) with the help of folic acid, vitamin B12, and vitamin B6. This transformation utilizes a set of mediator molecules (called enzymes) and happens via a delicate sequence of specific steps.
Learn more about: B12
Therefore, insufficient amounts of these vitamins in the body can hamper the natural breakdown of homocysteine. In addition, if there are any deficiencies in the mediator molecules, the breakdown is also hampered. This can cause homocysteine to accumulate in the blood because its breakdown is slow and inadequate.
Can elevated homocysteine levels be genetic?
Homocysteine levels in the blood may be elevated for many reasons as briefly described in the above section. More specifically, these can be divided into severe genetic causes and other milder causes.
In the genetic condition called homocystinuria, there is a deficiency or lack of an important mediator molecule (enzymes) in the complicated homocysteine breakdown pathway. This leads to severely elevated levels of homocysteine. In this rare and serious condition, there is a constellation of symptoms that include developmental delay, osteoporosis (thin bones), visual abnormalities, formation of blood clots, and advanced atherosclerosis (narrowing and hardening of blood vessels). This condition is mainly recognized in childhood.
Milder genetic variations are more common causes of elevated homocysteine levels (hyperhomocysteinemia). In these conditions, the mediator molecules malfunction and are less efficient because of minor abnormality in their structure. They also lead to elevation of homocysteine levels, although much milder than in homocystinuria, by slowing down the breakdown of homocysteine.
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