The 21-time Grand Slam champion has withdrawn from the China Open, which starts on Saturday, and the season-ending Women's Tennis Association finals in Singapore.
Williams, 34, missed the chance to seal a calendar Grand Slam when she lost in the US Open semi-finals in September.
"It's no secret I've played injured most of the year," said the American.
"Whether it was my elbow, my knee, or, in the final moments after a certain match in Flushing (Meadows), my heart."
She added: "I am taking a proactive step and withdrawing from tournaments in Beijing and Singapore to properly address my health and take the time to heal."
