This paper describes the case of a 77-year-old woman who presented to our dental hospital with spontaneous gingival bleeding. Furthermore, the patient had moderate to severe generalized marginal periodontitis, with a plaque score of 100% and a bleeding rate of 88% during probing, indicating poor oral hygiene. Blood tests revealed mild thrombocytopenia（138,000/μL, reference value：140,000-379,000/μL）, slight prolongation of PT-INR（1.22, reference value：0.90-1.13）and APTT（45.7, reference value：24.0-34.0）, and abnormal findings of total serum protein（10.4 g/dL, reference value：6.5-8.2 g/dL）. However, hemostatic function was within an acceptable range. Consequently, a tooth extraction was performed, and hemostasis was achieved through suturing and the use of a stent. Subsequently, the patient was referred to a hematologist. Further examination revealed an elevated serum IgM level of 7,077 mg/L（reference value：52-270 mg/dL）and an increasedβ2-microglobulin level of 2.6 mg/L（reference value：0.9-1.9 mg/L）, leading to a diagnosis of macroglobulinemia. It is considered that consultation with a hematologist is crucial in cases of unexplained elevation of total protein and challenges in controlling gingival bleeding in older adults, even though the“Guidelines for Dental Extractions in Patients Receiving Antithrombotic Therapy, 2020 Edition”does not specifically address this condition. Additionally, cases with poor oral hygiene and serum IgM level exceeding 3,000 mg/dL, having high risk of post-extraction bleeding, require priority treatment with plasma exchange.