I'm having a problem. there are some dark blue veins on my breasts.

Get seen by a doctor: You need a doctor to determine if they are new onsent, painful, painless, normal, etc. Clinical breast examination, risks for breast disease, etc. They can be either normal or a sign of a medical condition. You should get seen by a physician.

Normal finding: I am amazed about how often I have women ask me about the veins on their breast. Occasionally they are spider veins but mostly they are blue veins. These are almost always normal findings and normal variations of chest veins. They tend to be more pronounced in fair skinned females and they may be related to hereditary factors or even pregnancies. No treatment is necessary unless for cosmetics.