Cystine (Plasma)

Optimal Result: 13.4 - 51.9 nmol/ML.

Cystine is rate limiting for glutathione production. Cystine is the oxidized form of cysteine.

Cystine is formed from the oxidation of cysteine, or from the degradation of glutathione oxidation products. It is two cysteines linked together with a disulfide bond.

- Low cystine may be reflective of reduced glutathione levels and has also been noted in those with celiac disease and lower BMD.

- Cysteine can be imported into cells either directly or as cystine, within the cell, cystine is immediately reduced to cysteine.

- Higher plasma cystine has been associated with older age, female, higher BMI, lower GFR, diabetes mellitus, metabolic syndrome, hypertension, lower total cholesterol levels, statin use, lower ejection fraction, and higher hsCRP.

- Higher urine cystine may be indicative of impaired amino acid reabsorption defects and has been associated with recurrent cystine kidney stones.

- Cystine from foods sources is considered nutritionally equivalent to cysteine (egg, beef, and whole grains, fish, lentils, and oatmeal).


- Go YM, Jones DP. Redox theory of aging: implications for health and disease. Clin Sci. 2017;131(14):1669-1688.

- Dall’Acqua S, Stocchero M, Boschiero I, et al. New findings on the in vivo antioxidant activity of Curcuma longa extract by an integrated (1)H NMR and HPLC-MS metabolomic approach. Fitoterapia. 2016;109:125-131.

- Woodard LE, Welch RC, Veach RA, et al. Metabolic consequences of cystinuria. BMC Nephrol. 2019;20(1):227.

- Brantley MA, Jr., Osborn MP, Sanders BJ, et al. The short-term effects of antioxidant and zinc supplements on oxidative stress biomarker levels in plasma: a pilot investigation. Am J Ophthalmol. 2012;153(6):1104-1109.e1102.

- Hopkins MH, Fedirko V, Jones DP, Terry PD, Bostick RM. Antioxidant micronutrients and biomarkers of oxidative stress and inflammation in colorectal adenoma patients: results from a randomized, controlled clinical trial. Cancer Epidemiol Biomarkers Prev. 2010;19(3):850 858.

- Leslie SW, Sajjad H, Nazzal L. Renal Calculi (Cystinuria, Cystine Stones). In: StatPearls. Treasure Island (FL): StatPearls Publishing LLC.;2020

- Birwe H, Schneeberger W, Hesse A. Investigations of the efficacy of ascorbic acid therapy in cystinuria. Urolog Res. 1991;19(3):199-201.

- Brundig P, Borner RH, Berg W, et al. [Possibilities and limits in the treatment of cystine calculus diathesis with high-dose ascorbic acid. Results of a combined study with 17 patients]. Zeitschrift Urol Nephrol. 1986;79(3):137-146.

- Lux B, May P. Long-term observation of young cystinuric patients under ascorbic acid therapy. Urolog Internat. 1983;38(2):91-94.

- Asper R, Schmucki O. [Cystinuria therapy by ascorbic acid (author’s transl)]. Urolog Internat. 1982;37(2):91-109.

What does it mean if your Cystine (Plasma) result is too high?

Anything that elevates cysteine, could potentially contribute to higher levels of cystine.

Elevations of cystine may be associated with increased oxidative stress; antioxidants such as vitamins A, C, E and plant- based antioxidants may be considered.

In plasma, cystine is increased with age, obesity, cigarette smoking, alcohol abuse, HIV infection, carotid intima media thickness, endothelial cell function, type 2 diabetes, and age- related macular degeneration.

Cystinuria is an inherited renal transport disorder that features poor renal conservation and increased urinary excretion of cystine and other amino acids and metabolites. This condition is associated with renal calculi formation. Genova’s profiles are not meant to diagnose inherited cystinuria. If suspected, due diligence with conventional medicine work up is recommended.

What does it mean if your Cystine (Plasma) result is too low?

Anything that may lower cysteine, could potentially contribute to low cystine levels. Low cystine may be seen specifically in low animal protein diets.

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