Semen can indicate the health status of men

Besides sperm, semen is made up of 65 per cent of fluid from the seminal vesicles, 30 to 35 per cent from the prostate and 5 per cent from the vasa. Semen contains citric acid, free amino acids, fructose, enzymes, phosphorylcholine, prostaglandin, potassium, and zinc. The amount of semen produced varies from a few drops to about 6 ml.

One amount of ejaculate may contain between 40 million to 600 million sperm depending on the volume and the length of time stored before ejaculating. Yet, the quantity of sperm produced will only cover the head of a pin. Samples used for medical study are obtained by requiring the donor to masturbate, or if a sample cannot managed without intercourse, then non-reactive condoms can be used.

Normal Semen
The Look: Semen is usually a cloudy white fluid that within 30 minutes becomes runny and clear.

The Smell: Chlorine type smell in semen is normal.

The Taste: Slightly sweet due to fructose. The taste of semen tends to change slightly from person to person.

What is Considered Abnormal Semen?
Low Volume of Ejaculate

A decrease in semen, or an absence of semen from the seminal vesicle, can sometimes be due to a blockage.

Watery Semen

Watery semen is usually a sign of retrograde ejaculationin which the ejaculate goes backwards into the bladder. This is not dangerous, but abnormal liquefaction of semen may also be caused by prostate abnormalities, such as prostatitis.

Thick or Lumpy Semen

The viscosity of semen can vary for a number of different reasons. Consistently thick semen does restrict the ability of the sperm to move about, so this can be important if you and your partner are trying for a baby. Volume may also be low due to low hydration, fluids used up during sex may result in a small amount of ejaculate, or if you repeat the sex act and/or ejaculate in a short period of time this will also effect the amount produced. Volume and sperm production can decline with age, but potency is not necessarily affected. If you are concerned do consult your doctor especially in the case of:

Red or Brown Colored Semen

If your semen is stained with a red or brown colored fluid it may be caused by blood. Sometimes a small blood vessel may burst when you ejaculate. Within a day or two the semen should return to its normal state, so there should be no need to worry. If it continues then you should see your doctor. Blood in semen may be present for many different reasons, such as infection, trauma and sometimes, but rarely, cancer.

Yellowish or Green Colored Semen

Normal semen may have an off-white or yellow hint to the color. Where semen is uncharacteristically yellow or greenish in color it is a sign of infection, often due to a sexually transmitted disease called gonorrhea. Go to your local STD clinic. If it is gohorrhea, treatment is simple with the use of antibiotics.

Foul Smelling Semen

Foul smelling semen is nearly always a sign of infection. Go and see your doctor.

Source: About.com