Based on the Sperm Analysis course developed by Laura E. A. Cook, M.D., Jan A. Enabore, and William E. Roudebush, Ph.D., HCLD — Department of Biomedical Sciences, University of South Carolina School of Medicine Greenville

When a couple is having difficulty conceiving, a semen analysis is one of the first and most important diagnostic steps. Although infertility is commonly felt to be a female condition, a male factor often plays a significant role. Understanding what a semen analysis measures — and what the results mean — is an important part of navigating a fertility evaluation.

Editor’s Note: Statistics indicate that approximately 40% of infertility cases are attributed to female factors, 40% to male factors, and the remaining 20% to unexplained infertility. (Source: American Society for Reproductive Medicine)

What Is a Semen Analysis?

A semen analysis is the study of an ejaculate sample from a male. These studies are done in order to determine if there are any abnormalities in the semen or spermatozoa (sperm cell) that might prevent successful impregnation.

Certain risk factors place a male at higher risk of having infertility, including abnormalities or issues with the testicles themselves, prior treatment for cancer, hormonal disorders, prior scrotal surgery, or infections such as a sexually transmitted disease.

How Is the Sample Collected?

Semen samples are normally collected via masturbation. Ideally the sample is collected in a private room near the laboratory where the analysis is to be completed. If this is not an option, the sample must be brought to the laboratory within 60 minutes of collection.

For patients who cannot give a sample via masturbation, a physician or laboratory may supply a special condom to collect the sample. Coitus interruptus (the withdrawal method) is an unacceptable method to obtain a sample — the first portions of ejaculate contain the highest concentration of sperm and may be lost using this method.

Preparing for the Test

Proper preparation is essential for an accurate result:

• Patients must abstain from sex or masturbation for more than 48 hours, but less than 7 days, for an optimal semen sample.
• Sperm count can be affected when the male has ejaculated less than 48 hours prior to giving a sample.
• Motility and vitality of sperm can be affected when the male has not ejaculated for greater than 7 days.
• Samples are collected in a clean, wide-mouth container and stored at warm temperatures of 20–40 degrees Celsius to maintain sperm motility.
  

  Figure 1. A clinical laboratory somatic cell (sperm counting)

  Figure 2. Analysis of the sperm sample

What Does Analysis Measure

1. Liquefaction

Liquefaction is the process in which a semen sample liquefies or becomes less viscous. Normal semen samples liquefy within 60 minutes at room temperature, but often liquefaction is complete within 15 minutes. It is important for the analysis that the sample becomes liquefied.

If complete liquefaction does not occur within 1 hour, additional treatment such as mechanical mixing or enzyme digestion may be necessary.

2. Viscosity

A liquid is described as viscous if it flows very slowly or is thick. Viscosity of a semen sample affects both the function and ability of sperm to reach a female egg, as well as the ability for a technician to analyze the sample.

Figure 3. Viscosity is determined by drawing up some of the sample into a pipette and observing the speed of flow and how it drips with gravity. Normal semen viscosity drips from the pipette in small drops, while semen with abnormal viscosity drips in longer threads greater than 2 centimeters in length.

Figure 4. Normal semen viscosity drips from the pipette in small drops

Figure 5. Abnormal viscosity drips in longer threads greater than 2 centimeters in length

3. Volume

Volume of the sample is an important component of a semen analysis. Low semen volume may contain a low sperm count, which decreases the likelihood of pregnancy. A normal volume of semen is greater than 2 milliliters.

4. pH

The pH value is a unit of measurement to determine how acidic a fluid is. The pH scale ranges from 0 to 14, with 7 being neutral. The pH of semen is important for normal biological function and survival of sperm.

The pH of the female vagina is an acidic environment, while the pH of normal semen is basic. Survival of sperm within the vagina therefore relies upon a normal basic pH of semen.

A normal pH of semen is greater than or equal to 7.2. A pH of less than 7.0 in a sample that contains no sperm can indicate an ejaculatory duct obstruction or bilateral congenital absence of vas deferens — a tube that transports sperm from the testicles to the urethra for ejaculation — thus preventing sperm from being released from the testicles and successful conception.

The pH of semen is measured within one hour of ejaculation via a single drop sample onto pH indicator paper.

Figure 7. A single drop of semen sample being placed onto pH indicator paper

Figure 8. pH paper turned blue, indicating a normal basic pH ≥ 7.5

5. Appearance (Microscopic Analysis)

A semen sample must be visualized using a microscope. The sample must be visualized within an hour of collection, while the sample is liquefied. The andrologist — a highly trained laboratory technician who studies male reproduction — observes how sperm in the sample vary in:

• Number (concentration and total count)
• Color
• Shape (morphology)
• Motility — the speed and direction of movement of the sperm

Figure 9a. Microscope setup for semen analysis	Figure 9b. Microscope slide preparation
Figure 9c. Semen sample on slide under microscope	Figure 9d. Microscopic view of sperm

Normal Reference Values

The following tables present the original course reference values (WHO 5th Edition, 2010) alongside the updated values (WHO 6th Edition, 2021). The core parameters have not changed — some thresholds have been refined as more data became available.

* Values shown in red ↓ indicate parameters where the 2021 threshold was lowered from the 2010 edition.

* It is commonly accepted that a semen sample with less than 4% of sperm cells with normal morphology is likely to have decreased fertility.

* It is commonly accepted that a semen sample with less than 4% of sperm cells with normal morphology is likely to have decreased fertility.

What Happens If Results Are Abnormal? — Understanding IUI

If a semen analysis reveals abnormalities, one treatment option is intrauterine insemination (IUI). Intrauterine insemination is a procedure in which the male’s semen specimen is “washed” and then inserted directly into the female’s uterus just prior to ovulation, in order to improve the likelihood of conception.

The “washing” procedure effectively removes the viscous seminal fluid and subsequently enhances sperm motility. IUI is a less invasive procedure, as well as more cost effective, than in vitro fertilization (IVF).

A Clinical Example: The Case of Mr. Simpson

To illustrate how semen analysis results are interpreted, consider this case. Mr. Simpson’s semen was found to have delayed liquefaction (greater than 1 hour) which also resulted in a high degree of viscosity — a seminal fluid thread length of over 3 cm.

He had normal morphology of sperm. His semen showed a pH of 7.5, a normal value. Most likely due to the high viscosity, his specimen had only 25% sperm motility with only 10% progressive motility. He had normal sperm count and concentration.

It was therefore assumed that due to a lack of liquefaction and high viscosity, his spermatozoa were unable to effectively reach the female egg for fertilization. The couple was recommended to have a maximum of three intrauterine insemination (IUI) procedures. After their second IUI attempt, the couple had a successful conception.

Take the Full Interactive Course

INCIID offers a complete interactive course on sperm analysis and the male reproductive system, developed by physicians and scientists at the University of South Carolina School of Medicine Greenville. The course includes visual demonstrations of the analysis process, reference value tables, and a clinical case study.

Editor’s Note — 2026 Update:

The core components of a semen analysis described in this course — liquefaction, viscosity, volume, pH, motility, morphology, and concentration — remain the foundation of male fertility evaluation and are still assessed in clinics worldwide today. However, two important developments have occurred since this course was produced.

Updated Reference Values: The WHO published its sixth edition laboratory manual in July 2021, updating some of the reference ranges used in clinical practice. Notably, the six-edition simplified sperm motility grading to two grades (A and B) from the previous four-grade system, making assessments easier to understand and more standardized. PubMed CentralJomh

Technology Advances: Many fertility clinics now use Computer-Assisted Sperm Analysis (CASA) — automated systems that use computer algorithms and imaging technology to assess sperm count, motility, and morphology with greater precision and consistency than manual microscope analysis alone. Advances in artificial intelligence are further transforming sperm analysis, with AI-enhanced CASA systems now able to detect subtle patterns not easily discernible by human observation. nihThe Kingsley Clinic

This article provides a foundational overview of what is measured and why — the parameters themselves have not changed. For information on advanced sperm tracking technology, see INCIID’s article on the STAR (Sperm Tracking and Recovery) System 

References

WHO Laboratory Manual for the Examination and Processing of Human Semen, 5th Edition. World Health Organization. Cambridge, UK: Press Syndicate of the University of Cambridge, 2010.

Course content developed by Laura E. A. Cook, M.D., Jan A. Enabore, and William E. Roudebush, Ph.D., HCLD — Department of Biomedical Sciences, University of South Carolina School of Medicine Greenville, Greenville, SC, USA. All Rights Reserved © INCIID.

INCIID thanks and appreciates the students and faculty of the University of South Carolina School of Medicine and Drs. Laura Cook and Bill Roudebush for their help and support in the education of patients.

Questions or requests? Contact INCIID