Homocysteine (HCY) Lab Values

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Determine the significance and clinical use of measuring Homocysteine in clinical practice


Lab Test Name:




Homocysteine is a type of amino acid. Your body naturally makes it. But at high levels, it can damage the lining of arteries and can encourage blood clotting. This may raise your risk for coronary artery disease, heart attacks, blood clots, and stroke



Its evaluation is useful in: 

  • Cardiovascular disease
  • Venous thromboembolism
  • Evaluate for vitamin B12, vitamin B6 and folate deficiency 
  • Diagnose homocystinuria- a rare inherited disorder that interferes with the body breaking down and processing amino acids.


Normal Therapeutic Values:

Normal –  5 to 15 mmol/L


  •  Plasma separator tube


What would cause increased levels?


  • >15 mmol/L 
  • Vitamin B12, B6, and folate deficiencies
  • Homocystinuria
  • Kidney disease- impaired metabolism and decreased excretion
  • Hypothyroidism
  • Medications- PPIs, cholesterol-lowering medications
  • Psoriasis
  • SLE
  • Smoking


What would cause decreased levels?

  • Folic acid- treatment
  • High fiber diet
  • Nutrient-rich diet
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Hey everyone, Abby, here from nursing.com. In this lesson, we’ll talk about homocysteine and when we might see this lab drawn, its normal values, and what might cause it to be increased or decreased in the body. Let’s get started! 


Homocysteine is a lab value that measures the amount of home assisting in the blood home. Homocysteine is an amino acid that is synthesized by the body and can really cause vessel damage. And with vessel damage, what do we see? Coronary artery disease, there could even be myocardial infarction, blood clots, like this crazy thing right here and, lead to stroke. So, what are some clinical indications for why we would draw this lab? Well, just like we just talked about, it’s to evaluate cardiovascular disease and also venous thromboembolisms. It evaluates it for if, uh, deficiency in vitamins B12, and B6, and if there’s a folate deficiency. It’s also used to diagnose homocystinuria. 


Normal therapeutic values are between five and 15 millimoles per liter, and it’s collected in a plasma separator tube. Lab values when they’re increased, anything greater than 15 millimoles per liter are going to indicate a deficiency in nutrients, like vitamin B12, vitamin B6, and folate. This, uh, homocystinuria is a really rare disease where the body isn’t actually able to process amino acids, and this lab will be increased in the presence of this rare disease. It’s also going to increase in kidney disease, hypothyroidism, due to certain medications, psoriasis, lupus, and even smoking. A lot of this, I attribute to inflammation. It will be decreased if there’s a resolution,  so a resolution would be supplementation of those nutrient deficiencies like folic acid, vitamin B12, and vitamin B6. It can also be attributed to a high fiber, nutrient rich diet. Those are good things. 


To wrap this up, homocysteine is a measurement in the blood to evaluate for the risk of blood clots, cardiovascular disease, and to diagnose homocystinuria. Normal values are between five and 15 millimoles per liter. An increased value is going to be greater than the 15 millimoles per liter and indicates that there’s a deficiency in either vitamin B12, B6, or folate. It’s also going to increase in homocystinuria. Decreased values are due to a balanced diet with plenty of fiber and those vitamins and nutrients that we talked about. 


Now, you have all done a great job on this lesson. This wraps it up. We love you guys, now go out and be your best self today and as always, happy nursing.


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