What is considered low sperm count?

This has been a moving target over the years, and additionally, there are multiple numbers that are often called the “count,” like concentration, total sperm count, and total motile sperm count.  The criteria for what is considered a normal semen analysis are set by the World Health Organization. They are now in the sixth edition of the WHO manual for semen analysis, which was published in 2021 – here is the full text: https://www.who.int/publications/i/item/9789240030787.  The latest low-end cutoffs for a normal semen analysis are a volume of 1.4 mL, a sperm concentration of 16 million/mL, sperm motility of 42%, and strict morphology of 4%. Keep in mind that these cutoffs don’t determine normal or abnormal, or fertile or infertile; these numbers are all on a long continuum of normal fertility. The cut-offs for each low parameter come from a large study of normally fertile men who have recently caused a pregnancy, and the cut-offs are somewhat arbitrarily determined to be drawn at the 5th percentile of normal. If each parameter is plotted on a bell curve of normal, the cutoffs are on the lower end of the curve, but these are still coming from men who successfully caused a pregnancy. The more parameters that are abnormal, the more likely the problem is significant; on the contrary, if only one or two parameters are abnormal, this is less severe. There is an important calculation that most patients should understand: the volume, multiplied by the concentration, gives a total sperm count; and the total sperm count multiplied by the percentage of motile sperm, gives a total motile sperm count. The total motile sperm count, or TMC, is, therefore, the best summary number from a semen analysis, and the best way to compare one sample from another. An average normal TMC for a fertile male is around 100 million, and an accepted low cutoff for the number needed to conceive naturally is around 30 million. A low number would be 10-30 million TMC, which is typically what is required for intrauterine insemination (IUI). When TMC’s are less than 10 million, this is a severely low count, and this is a count that is in range only for IVF. We only need one sperm per egg for IVF, so a typical IVF range goes from rare sperm identified in the ejaculate all the way up to around 10 million TMC.  You’ll notice I’m not talking much about sperm morphology; this is a larger discussion, but in general, this is the least important parameter compared with volume, concentration, motility, and total motile counts.