What is causing my bald patches? I'm female, 20 years old (Photo)

You need to see a doctor for a proper exam if you want a proper diagnosis. You need more than just a photo to find the cause for your hair loss. Afterwards you can think about treatment.

The most likely cause is alopecia areata although a few other diagnoses are possible.You'll want to see a dermatologist for diagnosis. If your periods are regular there are three blood tests you need as well: CBC, TSH and ferritin (the iron test). Whether or not any other blood tests are worthwhile to order depends on the answers you provide to some pretty detailed questions.An experienced dermatologist can diagnose your hair loss with an up close examination.

I would worry about the disease alopecia areata as well as genetic hair loss which runs in families on the woman's side
(mother, sister, grandmothers etc...), but most female hair loss occurs because
of some underlying cause such as birth control pills, some medications that are
used, and a variety of other diseases that shock the hair into miniaturization.
A typical knowledgeable doctor will examine you, determine the distribution of
your hair loss, see if it is uniform or patchy, take a careful history from you
and order a variety of blood tests to include the following. You must see a
good doctor for this assessment:


Sex Hormone tests

SHBG (Sex Hormone
Binding Globulin) used to test status of male hormones

Estradiol is a sex
hormone

FSH (Follicle
Stimulating Hormone) *not hair follicle but follicle in the ovary*

LH (Luteinizing
Hormone) is a sex hormone

Free Testosterone

Total Testosterone

ANA (Anti Nuclear
Antibody) used to test for Lupus or other autoimmune diseases

TSH (Thyroid
Stimulating Hormone) used to test for hyper or hypo-thyroid disease

Test Iron status

TIBC (Total Iron
Binding Capacity)

Ferritin

Iron