L-cysteine is a type of amino acid, which are the building blocks of proteins. The body makes L-cysteine from another amino acid called methionine.

L-cysteine is naturally found in foods, but because it's made in the body it doesn't need to be consumed in the diet. L-cysteine has antioxidant effects and is used to make up antioxidants such as glutathione.

People use L-cysteine for cancer, diabetes, hangover, stroke, and many other conditions, but there is no good scientific evidence to support these uses.

Don't confuse L-cysteine with N-Acetyl Cysteine (NAC). These are not the same.
When taken by mouth: L-cysteine is commonly consumed in foods. But there isn't enough reliable information to know if L-cysteine is safe when used in larger amounts as medicine or what the side effects might be.

Special Precautions & Warnings:

Pregnancy and breast-feeding: L-cysteine is commonly consumed in foods. But there isn't enough reliable information to know if L-cysteine is safe to use in larger amounts as medicine while pregnant or breast-feeding. Stay on the safe side and avoid use.

Surgery: L-cysteine might interfere with blood sugar control during surgery. Stop taking L-cysteine at least 2 weeks before a scheduled surgery.


There is interest in using L-cysteine for a number of purposes, but there isn't enough reliable information to say whether it might be helpful.
Likely effective Effectiveness definitions
Possibly effective Effectiveness definitions
Likely ineffective Effectiveness definitions
Possibly ineffective Effectiveness definitions
Insufficient evidence Effectiveness definitions

Dosing & administration

L-cysteine is naturally found in foods. But as medicine, there isn't enough reliable information to know what an appropriate dose of L-cysteine might be. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult a healthcare professional before using.

Interactions with pharmaceuticals

Medications for diabetes (Antidiabetes drugs)

Interaction Rating=Moderate Be cautious with this combination.

L-cysteine might lower blood sugar levels. Taking L-cysteine along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.

Interactions with herbs & supplements

Herbs and supplements that might lower blood sugar: L-cysteine might lower blood sugar. Taking it with other supplements with similar effects might lower blood sugar too much. Examples of supplements with this effect include aloe, bitter melon, cassia cinnamon, chromium, and prickly pear cactus.

Interactions with foods

There are no known interactions with foods.

BioMedica VegeNAC is a practitioner product.

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