OBJECTIVES: Patients with chronic constipation (CC) are often treated with diverse over the counter (OTC) laxatives, bulking agents, stool softeners, and a limited choice of prescription (Rx) drugs. Sub-optimal treatment often results in adverse medical events or treatment modifications. The purpose of this study is to estimate healthcare resource utilization (HRU) and costs of such unmet treatment needs. METHODS: Data from the Missouri Medicaid program covering medical services and Rx and OTC medications (1997-2010) were used to select adult patients with CC receiving constipation treatments. The index date was defined as the date of the first constipation-treatment claim. Indicators of unmet treatment needs were observed during the one-year period after the index date and defined as the following events occurring while on constipation treatment: 1) switch to or addition of a new constipation treatment; 2) constipation-related inpatient (IP) or emergency room (ER) admission; 3) megacolon or fecal impaction diagnosis; 4) constipation-related surgery/medical procedure; or 5) use of other unusual constipation treatments. Incremental HRU and costs (USD 2010; measured from a public-payer perspective) were compared between patients with and without indicators of unmet needs using multivariate generalized linear regression models. RESULTS: A total of 8745 patients with CC were identified; 54.9% of them were found to have unmet needs during the one-year period following the index date. After adjusting for baseline differences, indicators of unmet needs were associated with more HRU, especially the number of IP days (IRR= 1.54; P<0.001) and ER admissions (IRR=1.35; P<0.001). Indicators of unmet needs were associated with a $2,978 incremental total annual healthcare costs (P<0.001) compared to patients without indicators of unmet needs. The cost difference was mainly driven by IP ($2,575 vs. $1,534; P<0.001) and pharmacy ($7,114 vs. $5,929; P<0.001) costs. CONCLUSIONS: Unmet treatment needs among CC patients were associated with a significant economic burden.