2-Hydroxyisocaproic acid (aka Leucic acid / α-hydroxyisocaproic acid / HICA) is a metabolite of the branched-chain amino acid leucine.

Moderate increase may result from: 

- Lactic acidosis - Lactic acidosis is a form of metabolic acidosis that begins when a person overproduces or underutilizes lactic acid, and their body is not able to adjust to these changes. People with lactic acidosis have problems with their liver (and sometimes their kidneys) being able to remove excess acid from their body.

- Episodic ketosis - when you go on a very high protein, severely carbohydrate-restricted diet. Your body becomes starved for glucose. Ketosis is your body's way of making up for this lack of fuel. Ketosis increases acids in your bloodstream. Episodic ketosis can lead to kidney damage and increase risk of cardiovascular disease.

- Deficiencies of the vitamins B1 (thiamine) or lipoic acid.

Potential treatment options:

People with slight to moderate elevations may use dietary supplements containing thiamine to improve clinical symptoms. 

Elevated 2-hydroxyisocaproic acid in urine has also been linked to short bowel syndrome. It may also be an indicator of oxidative stress. 

Significant elevations are associated with:

- Maple syrup urine disease (MSUD). MSUD is an autosomal recessive metabolic disorder affecting branched-chain amino acids. It is one type of organic acidemia. The condition gets its name from the distinctive sweet odor of affected infants' urine, particularly prior to diagnosis, and during times of acute illness.

- Pyruvate dehydrogenase deficiency. Pyruvate dehydrogenase deficiency (PDHD) is a rare neurometabolic disorder characterized by a wide range of clinical signs with metabolic and neurological components of varying severity. Manifestations range from often fatal, severe, neonatal lactic acidosis to later-onset neurological disorders.