Howell received a BA from Park College in Parkville, Missouri in 1944, and an MD from McGill University in 1949. She interned at Children's Memorial Hospital in Montreal, Canada, and then came to Duke in 1951 as a senior assistant resident in pediatrics-in 1970 she would be the first female to be given the Distinguished Duke Medical Alumni Award. In 1952 she was a research fellow in hematology at Harvard. She returned to Duke in 1955 and served as a pediatric hematologist working with pediatric cancer patients until 1963 when she left to become chair of Pediatrics at the Medical College of Pennsylvania. She would also become chair of the Department of Family and Community Medicine at the University of California, San Diego in 1974.
Dr. Howell has been a pioneer in the hospice movement since 1968. She served on the Hospice Board of Directors since its inception and was instrumental in founding San Diego Hospice, of which she was named Director Emerita in 1989. Since her retirement, Dr. Howell established the Doris A. Howell Foundation for Research in Women's Health, which gives research grants to scholars in the area of women's healthcare and research. She has been given numerous awards, including the Salvation Army Woman of Distinction Award, the Humanism Award from the Health Care Foundation of New Jersey, and awards for leadership and service from the American Academy of Pediatrics. She has been listed in Who's Who in American Women.