NATURE OF BUSINESS	9 Months Ended
NATURE OF BUSINESS	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF BUSINESS	NATURE OF BUSINESS Axcella Health Inc. and subsidiaries ("Axcella," the "Company" or "we") is a biotechnology company that was incorporated in Delaware on August 27, 2008 and has a principal place of business in Cambridge, Massachusetts. The Company is focused on pioneering a new approach to treat complex diseases and improve health using endogenous metabolic modulator, or EMM, compositions. The Company's product candidates are comprised of multiple EMMs that are engineered in distinct combinations and ratios with the goal of simultaneously impacting multiple biological pathways. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, successful development of technology, obtaining additional funding, protection of proprietary technology, compliance with government regulations, risks of failure of preclinical studies, Clinical Studies and Clinical Trials, the need to obtain marketing approval for its product candidates, if required, and successfully market products, fluctuations in operating results, economic pressure impacting therapeutic pricing, dependence on key personnel, risks associated with changes in technologies, development by competitors of technological innovations and the ability to scale manufacturing to large scale production. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and any necessary regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. The accompanying condensed consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has historically funded its operations with proceeds from sales of preferred and common stock and borrowings under a loan and security agreement. As of September 30, 2020, the Company had an accumulated deficit of $257.4 million. The Company expects to continue to generate operating losses in the foreseeable future. The Company expects that its cash and cash equivalents at September 30, 2020 will be sufficient to fund its operations for at least the next twelve months from the date of the issuance of these interim condensed consolidated financial statements. The COVID-19 pandemic has spread globally, including to the United States and European countries, which has resulted in significant governmental measures being implemented to control the spread of the virus, including quarantines, travel restrictions, business shutdowns and clinical site closures to non-essential care and clinical trials. Although we cannot presently predict the scope and severity of COVID-19, these developments and measures could materially and adversely affect our business, our results of operations and financial condition, particularly if the COVID-19 pandemic adversely impacts our ability to conduct and complete our ongoing Clinical Study and planned Clinical Trials in a timely manner or at all. Additionally, potential shutdowns of government agencies such as the Securities and Exchange Commission (the “SEC”) or the U.S. Food and Drug Administration (the "FDA") may limit our ability to raise capital and negatively impact our product development timelines. The Company considered the impact of COVID-19 on the assumptions and estimates used and determined that there were no material adverse impacts on the Company’s results of operations and financial position as of and for the three and nine months ended September 30, 2020. The full extent of the future impacts of COVID-19 on our operations is uncertain. A prolonged pandemic could have a material adverse impact on financial results and business operations of the Company, including the timing and ability of the Company to complete our ongoing Clinical Study and planned Clinical Trials and other efforts required to advance the development of our product candidates.