What is Cystine? High and low values | Lab results explained

Cystine is the oxidized disulfide form of cysteine (Cys) and is the predominant form of cysteine in the blood due to its greater relative stability. Cystine is derived from dietary protein and, end formed endogenously from cysteine.

Lower levels:

Cystine may be low as a result of dietary protein insufficiency, malabsorption or impaired methionine metabolism. Supplementation of cystine along with antioxidant nutrients, Nacetylcysteine, or cofactors involved in methionine metabolism may be beneficial. Cystine and N-acetylcysteine supplementation should be avoided in the presence of intestinal yeast overgrowth and definitely contraindicated for insulin-dependent diabetics.

Higher levels:

– High levels might be due to excessive dietary intake or impaired cystine metabolism. Converted to cysteine (reduced cystine) via a B2 and copper-dependent step. Cystine is a major component of tissue antioxidant mechanisms.

– Suspect oxidative stress if: Significantly elevated cystine, compared to cysteine (urine only)


The information on is NOT intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: