I am a 53 year old female and I noticed about 6 months ago that I do not have moons on my fingernails anymore... only small ones on my thumbs. I always had good sized moons on my nails until then. What does this mean?

Abnormal Nail Arc Shadows: The little white crescent at the base of each fingernail is known as a nail-arc shadow or "health circle." In a healthy person, each fingernail has a well-proportioned arc; arcs indicate not only one's general physical condition but the state of the cardiovascular function.

If the arcs are unusually large or asymmetrical, this may indicate high blood pressure; if one or more arcs are missing (out of the ten fingernails), this may suggest an imbalance in the nervous system or anemia. The arcs may become obscured and hard to see following a stroke, but they may also become small or obscured if there is gastrointestinal disease or ulcer, asthma, acute pneumonia, or gout.

I also found this:

Lunula

The Lunula is often referred to as “moons”. The lunula is in fact the front end of the matrix. The whitish half moons are keratin cells that have not yet been completely flattened and still have some of their content. Not everyone has visible lunula's The lunula is normally more prominent on the thumbs. The shape of the lunula determines the shape of the free edge/distal edge.

After have life saving surgery and lots of oxygen they appeared on every nail!

Well, I can not believe what I just read from the others. The #1 hand-surgeon in the USA, who I have not asked permission to use his name, who operated on both of my hands because of caparpal tunnel syndrome years ago, {with-in three weeks 100% usage back - prior I could not even hold a pencil}... And he is the developer of the now used Carpal Tunnel Release System, used by all the other hand doctors, developed with the 3M-Company. On the doctor first seeing me, he took my hands and looked at them. I had moons on all the fingers. First words out of his mouth were, "Calcium deficient Tom".. You need to take Calicum with magnesium & zinc, & in three months they will all go away. That was 20 years ago and to this day NO MOONS. I take that dossage daily. It is a sign from 'ones own body' that you are deficient in Calicum. Some people are dumb enough to believe it is the sign of new nails. Also, to help fingernail and hair growth, take Biotin... and a supplement of vitamin D; helps bones & immune system.