With changing lifestyle and dietary transition, there is an increase in intake of processed and packaged foods which tend to have a number of food additives. This has increased our consumption of these chemical substances. One of such additives is carrageenan (CGN) - E407. This paper reports the effect of 0.5 % carrageenan solution consumption on the main indices of endogenous intoxication in rats. Experimental studies were conducted on 48 non-linear, male, white rats weighing 180-200 g. The experimental animals had free access to 0.5% carrageenan solution (Sigma-Aldrich, USA) in drinking water. Control group of animals received pure water. Syndrome of endogenous intoxication was evaluated using measurement of the middle mass molecules contents in blood serum. We have found that even the minimal intake of carrageenan, triggers the mechanisms of endogenous intoxication in rats, starting in 2 weeks of consumption. 1 month consumption of carrageenan with drinking water in concentration of 0.5% is associated with significant increase in endogenous intoxication, manifested by increased contents of middle mass molecules (both the chain amino acids and the aromatic amino acids) in blood serum. From these facts, one may conclude that although carrageenan has been used widely in food as an emulsifier, a stabilizer, and a thickener for more than 50 years, some questions of its safety are still opened.