Can you tell how long a tick has been attached to you?

You can estimate how long a tick has been attached to you by examining its size, engorgement level, and appearance, though exact timing is difficult without knowing when you were in tick habitat. Unfed ticks are flat and small, nymphs are poppy seed size and adults are apple seed size, and as they feed for 3 to 10 days they become engorged, swollen, and larger, changing color from brown to grayish blue. If tick is flat and small, it likely attached within last 24 hours, if slightly engorged and still relatively flat, 24 to 48 hours, if noticeably swollen and round, 48 to 72 hours or more, and if very swollen like small grape, it has been attached for many days and is fully engorged. This matters because risk of Lyme disease transmission increases after 36 hours of attachment, as Borrelia bacteria need time to migrate from tick gut to saliva, so if tick is flat, risk is low, if engorged, risk higher. However, engorgement estimates are approximate, as feeding rate varies by species and host. Other clues include scab formation around bite, but not reliable. Best way to know attachment time is recall when you were in tick habitat, for example if you hiked yesterday and find engorged tick today, it likely attached yesterday. Regardless of estimate, remove tick promptly with fine tipped tweezers, save tick in sealed bag with date, monitor for symptoms for 30 days, and see doctor if rash or flu-like symptoms appear.