A semen analysis measures the health and quantity of sperm in an ejaculate, giving a detailed picture of male fertility potential. It evaluates several factors at once: how many sperm are present, how well they move, whether they’re shaped normally, and whether the fluid itself has the right properties to support them. It’s typically the first test ordered when a couple has difficulty conceiving, and it can also confirm the success of a vasectomy.
How to Prepare for the Test
The accuracy of your results depends heavily on how you prepare. You’ll be asked to avoid any sexual activity that causes ejaculation for 2 to 3 days before the test, but not longer than 5 days. Too short a window and the count will be artificially low; too long and sperm quality starts to decline. The sample is usually collected by masturbation into a sterile cup, either at the clinic or at home if you can deliver it within a specified time (typically 30 to 60 minutes).
Sperm production naturally fluctuates from week to week based on stress, illness, heat exposure, alcohol use, and dozens of other variables. A single abnormal result doesn’t necessarily mean there’s a permanent problem. Most clinicians will repeat the test at least once, usually a few weeks later, before drawing conclusions.
Semen Volume and Physical Properties
Before anyone looks at the sperm themselves, the lab evaluates the semen as a fluid. The volume of the ejaculate is measured first. Low volume can point to a blockage in the reproductive tract, incomplete collection, or a problem with the glands that produce seminal fluid (the prostate and seminal vesicles).
The pH is checked next. Normal semen pH falls between 7.2 and 8.0. The prostate contributes acidic fluid while the seminal vesicles contribute alkaline fluid, so the final pH reflects the balance between the two. A pH below 7.2 can suggest a blockage of the seminal vesicles. A pH above 8.0 can indicate an infection somewhere in the reproductive tract.
The lab also notes how quickly the semen liquefies. Fresh semen starts out as a gel-like clot and gradually becomes liquid. This process takes about 25 minutes on average. If it takes significantly longer or the sample stays thick and viscous, it can trap sperm and prevent them from swimming freely, which matters for natural conception.
Sperm Count and Concentration
This is often the number people focus on most. The lab reports two related measurements: sperm concentration (how many sperm per milliliter of semen) and total sperm count (the concentration multiplied by the total volume). A concentration of roughly 15 million sperm per milliliter or more, with a total count of at least 39 million per ejaculate, has traditionally been considered within the normal range.
A very low count is called oligozoospermia. A complete absence of sperm is called azoospermia, which affects roughly 1% of all men and about 10 to 15% of men being evaluated for infertility. Azoospermia can result from a blockage preventing sperm from reaching the ejaculate, or from a problem with sperm production itself. These two causes require very different treatment paths, so further testing is needed to tell them apart.
Motility: How Well Sperm Move
Having enough sperm doesn’t help if they can’t swim effectively. Motility measures the percentage of sperm that are moving at all, while progressive motility specifically measures the percentage swimming forward in a sustained direction. Progressive motility is the more important number because sperm need to travel through the cervix, uterus, and fallopian tubes to reach an egg.
The standard thresholds are 40% or more for total motility and 32% or more for progressive motility. Sperm that vibrate in place without going anywhere (non-progressive motility) are counted as motile but contribute little to natural conception.
Many fertility specialists combine count and motility into a single figure called total motile sperm count, which represents the actual number of forward-moving sperm in the entire sample. This combined number is often more useful for predicting fertility than either measurement alone, and it helps guide decisions about whether treatments like intrauterine insemination or in vitro fertilization are more appropriate.
Morphology: Sperm Shape and Structure
Morphology evaluates the physical structure of individual sperm under a microscope: the size and shape of the head, the midpiece, and the tail. Under strict criteria (known as Kruger criteria), a normal result is 4% or more normally shaped sperm. That number sounds alarmingly low, but it reflects how stringently each sperm is graded. Even fertile men rarely have more than a small percentage of “perfect” sperm.
Head defects can affect the sperm’s ability to penetrate an egg. Midpiece defects can reduce the energy supply sperm need to swim. Tail defects impair movement directly. A very low morphology score, sometimes called teratozoospermia, doesn’t mean conception is impossible, but it lowers the odds with each cycle.
White Blood Cells and Signs of Infection
The lab also looks for round cells in the sample, which can be immature sperm cells or white blood cells. If white blood cells exceed 1 million per milliliter, the condition is called pyospermia, and it signals infection or inflammation in the reproductive tract. This matters because infections can damage sperm directly and because the inflammatory response itself produces reactive molecules that harm sperm DNA and membranes. Pyospermia is typically treatable with antibiotics or anti-inflammatory approaches once the underlying cause is identified.
What the Standard Test Cannot Tell You
A semen analysis provides a useful overview, but it has real limitations. There is significant overlap in sperm count, motility, and morphology between men who conceive naturally and men who don’t. A normal result doesn’t guarantee fertility, and an abnormal result doesn’t guarantee infertility.
The standard test also cannot detect damage to sperm DNA. Sperm can look normal under a microscope, swim well, and still carry fragmented DNA that affects fertilization, embryo development, and miscarriage risk. A separate test called a sperm DNA fragmentation assay measures this directly and is sometimes recommended when standard results look normal but conception still isn’t happening, or when there’s a history of unexplained miscarriage.
It’s also worth knowing that the World Health Organization’s most recent laboratory manual has moved away from rigid cutoff values that label semen as “normal” or “abnormal.” The reasoning is that fertility decisions are more complex than any single threshold can capture. Your results are best interpreted alongside your partner’s evaluation, your medical history, and how long you’ve been trying to conceive. The reference values still in widespread clinical use (the ones listed throughout this article) come from earlier editions and remain helpful as benchmarks, but they’re guidelines rather than hard boundaries.
Understanding Your Results
When you get your report back, you’ll see a table of numbers covering most or all of the parameters described above. Here’s a quick reference for the values clinicians commonly use:
- Volume: 1.5 mL or more
- pH: 7.2 to 8.0
- Sperm concentration: 15 million per mL or more
- Total sperm count: 39 million or more per ejaculate
- Total motility: 40% or more
- Progressive motility: 32% or more
- Normal morphology: 4% or more (strict criteria)
- White blood cells: fewer than 1 million per mL
- Liquefaction: complete within about 25 minutes
If one or more values fall below these benchmarks, it doesn’t necessarily point to a single cause. Temporary factors like a recent fever, heavy alcohol use, certain medications, or even a hot tub habit can suppress results for weeks. Sperm take roughly 74 days to fully develop, so anything that affected your health two to three months before the test can show up in your numbers. A repeat analysis after addressing any obvious lifestyle factors often looks different.