Fucoidan is a sulfated polysaccharide in the brown sea algae. This study was conducted in 20 subjects taking excessive fucoidan up to 4.05 g daily for 2 wk. They recorded questionnaire sheets about their health. Blood and urine were collected before and after 2 wk of ingestion. We found that no disorder was apparent in the test period. Although total cholesterol (P value 0.017) and low-density lipoprotein cholesterol (P value 0.017) showed statistically significant reduction and Cl (P value 0.002) showed significant increase, nothing deviated from the range of normal values. In conclusion, this study showed no abnormalities in the abdominal, fecal states, blood and urine at all.