Why do my gums bleed when I floss?
Gums usually bleed during flossing because plaque, the sticky bacterial film that collects at the gumline, has inflamed them. That inflammation is gingivitis, the early and often reversible stage of gum disease, and inflamed tissue bleeds easily on light contact. With daily flossing, bleeding from this cause should stop within a few weeks as the gums heal; bleeding that continues past that point needs an exam, not less flossing.
What the floss is touching
Plaque and tartar carry bacteria that trigger inflammation in the gums. The gums turn red, swollen, or tender, and bleed easily when floss or a brush touches them. When flossing is skipped, plaque collects between the teeth and gingivitis can develop quickly.
Left in place, plaque can harden into tartar, also called calculus. Floss cannot remove tartar; only a professional cleaning can, which is the limit of home care.
Why it should fade, and why stopping backfires
When you start flossing, the first passes reach gums that have been inflamed for a while, so bleeding is expected. Early gum disease caused by plaque can often be reversed by daily brushing and flossing, and the bleeding should stop within a few weeks as the tissue settles.
Stopping removes the step that clears plaque between the teeth, so the inflammation behind the bleeding stays. If the floss itself hurts, you may be forcing it too far into the gum; the oral hygiene guide covers technique.
Causes that are not plaque
Brushing too hard or with a worn, stiff brush can make gums bleed. Hormonal changes during pregnancy, puberty, menopause, or with birth control can cause bleeding regardless of how much plaque is present. Blood thinners, bleeding disorders, vitamin C or K deficiency, and uncontrolled or undiagnosed diabetes are other causes. Do not change a medication without talking to the prescriber.
Smoking works in the opposite direction. A study of about 12,400 adults found that smoking has a strong, dose-dependent suppressive effect on gum bleeding, so a smoker’s gums may bleed less even when inflamed. It is also the most significant risk factor for gum disease, so no bleeding is not reassurance.
When bleeding means you should be seen
See a dentist if your gums still bleed after a few weeks of consistent daily flossing, or if bleeding is new after years of regular flossing. Bleeding that comes with gums pulling away from the teeth so they look longer, loose or sensitive teeth, pain while chewing, or persistent bad breath points past early gingivitis; periodontal maintenance explains what that stage involves. Severe bleeding, or bleeding with other unexplained symptoms, also warrants a call to your physician.
Related treatments
General information, not dental advice. What is right for you depends on an examination.