Pre-ejaculate is a clear, slippery fluid almost exclusively produced by the bulbourethral glands that empty into the root of the penis. A tiny portion of pre-ejaculate includes mucus from the periurethral glands or Littre’s glands that line the urethra of the penis.
Pre-ejaculate usually released during sexual arousal/stimulation. When pre-ejaculate is released varies from one man to the next and varies between very early (before getting an erection) to late (at nearly the same time as ejaculation). Some may release pre-ejaculate prior to getting an erection (sometimes when simply holding hands or kissing). Other men release pre-ejaculate during an erection even if no penile stimulation is occurring. This can result in men noticing wet or dried streaks of pre-ejaculate fluid when waking in the morning after having multiple erections during the night. Many men notice pre-ejaculate fluid during foreplay or sexual stimulation while others may not notice any release as the fluid is released at nearly the same time as ejaculation.
Pre-ejaculate serves two main purposes – first it helps to flush the urethra of any remaining urine and to neutralize any acids that may affect the sperm as they pass through the urethra. Second, if it is released early enough, it provides a small amount of lubricant for the outside of the penis to reduce friction during intercourse. However, most men only produce a few drops of pre-ejaculate which is often insufficient for intercourse (the main lubricant for intercourse is produced by the periurethral glands of the woman, which can produce large amounts of lubricating fluid). Personal lubricants found over-the-counter are similar in consistency to pre-ejaculate fluid to aid in lubrication.
Some men wonder how much pre-ejaculate is normal. Most men report only seeing a few drops, but volumes up to 4ml (just under teaspoonful) can be considered normal. Very few clinical trials have been performed to measure pre-ejaculate volumes. In fact, a review of clinic studies has found only one trial that measured pre-ejaculate volumes. This was performed in 28 college age men. Pre-ejaculate volumes ranged from no pre-ejaculate on the low end, to 1ml of pre-ejaculate on the high end. No man in the study produced more than 1ml (~15 drops). The results were as follows:[i]
Long story short – about 1 in 25 men don’t have pre-ejaculate, 2 in 3 men release 1-3 drops, 1 in 4 men release 4-8 drops, and less than 1 in 25 release more than 10 drops. It was also noted that in some men who provided multiple samples over the study period had volumes that remained fairly consistent; however, some men had volumes that ranged from a couple of drops on time and up to 1 ml (15 drops) another time. This may have been due to poor handling (not catching all of the pre-ejaculate in the smaller sample or ejaculating some semen into the larger sample).
For disorders that affect the volume of pre-ejaculate, click HERE.
[i] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3564677/#R2 (12/20/2016)