Hair shedding during weight loss may have more than one contributor. Significant physical stress, illness, childbirth and restrictive diets can precede increased shedding. Hair loss is also listed among adverse reactions to approved semaglutide treatment.[1][3]

Shedding can follow a delayed timeline

Telogen effluvium is a form of increased shedding that can begin weeks or months after a trigger. That delay means the relevant history may start well before the week the shower drain looked different.[1]

Recent illness, surgery, changes in eating, weight change, childbirth and new medicines are worth mentioning. A person may also have an inherited thinning pattern alongside increased shedding.[1][2]

The scalp adds information

A dermatologist assesses where hair is being lost and examines the scalp for clues. They may also look at nails and other areas or gently check how hairs come away. Further tests depend on what the assessment suggests.[2]

Describe whether the change is diffuse, concentrated in a particular area or patchy. Mention pain, itching, redness or scaling as well as the amount of shedding.

Tests should answer a specific question

Blood tests may be appropriate when the findings suggest a medical condition, nutritional deficiency or hormone imbalance. A broad panel is not automatically required for everyone with shedding.[2]

During a medication review, information about appetite and food tolerance can help explain whether intake has changed substantially. It is also useful to say whether shedding began before treatment.

Rapid or patchy loss and symptoms affecting the scalp warrant a medical assessment.[1] For a gradual change, dated photographs and a short timeline can make the pattern easier to explain.