It is widely known that alcohol lowers blood sugar, but why does it? From an interesting study (CHARLES U. LOWE, LUIS L. MOSOVICH. The Paradoxical Effect of Alcohol on Carbohydrate Metabolism in Four Patients with Liver Glycogen Disease. Pediatrics, June 1965, VOLUME 35 / ISSUE 6.).
Oxidation of ethanol to acetaldehyde, the first step in alcohol metabolism, is catalyzed by the enzyme alcohol dehydrogenase and results in the reduction of DPN to DPNH. In a coupled reaction, pyruvate is converted to lactate with regeneration to DPN. There are a number of consequences of these reactions when alcohol is consumed. Lactate levels in blood rise; DPNH produced by the reaction inhibits the enzymatic steps involved in the conversion of UDP galactose to UDP glucose and glutamate to alpha keto glutarate. As a result of these inhibitions, galactose removal from blood is markedly delayed and gluconeogenesis from amino acids is inhibited.
This could help explain why people report easily getting plastered on Low Carb diets. A lack of dietary carbohydrates means that someone on a Low Carb is producing their blood glucose through Gluconeogenesis (GNG). If alcohol inhibits GNG then blood sugar may drop farther on a Low Carb diet than on a Higher Carb diet.