If you've been tired, flat, or losing ground in the gym, low testosterone is an easy thing to suspect. It's also easy to get the diagnosis wrong. A single test, taken at the wrong time of day, can make normal levels look low.
Testosterone changes through the day
Testosterone is usually highest in the morning and drops through the afternoon and evening. A blood draw at 4 p.m. can read noticeably lower than one at 8 a.m. on the same day.
That's why medical guidelines recommend measuring testosterone in the early morning, and confirming a low result with a second early-morning test on a different day before calling it low.
Many things can push a result down temporarily
A low number doesn't always mean a hormone problem. Levels can dip because of:
- A few nights of poor or short sleep
- A recent illness or infection
- Heavy drinking
- Significant weight gain
- Certain medications, including opioid pain medicines and steroids
Your physician will ask about these before reading too much into one result.
Total and free testosterone
Most testosterone in the blood is bound to proteins, mainly a protein called SHBG. "Total" testosterone counts all of it. "Free" testosterone is the small portion that isn't bound. When SHBG is unusually high or low, total testosterone alone can be misleading, so a careful workup often looks at both.
Symptoms matter as much as the number
Low testosterone is diagnosed when symptoms and consistently low lab results line up. Common symptoms include low libido, fatigue, loss of muscle, increased body fat and low mood. But each of those has other possible causes too, from thyroid problems and anemia to poor sleep and stress. A good evaluation checks for them at the same time.
Before treatment: what to talk about
If testosterone is confirmed low, there are a few things worth discussing with your physician before deciding on treatment:
- Fertility. Testosterone therapy can reduce sperm production. If you might want children, tell your physician, because other approaches may fit better.
- Monitoring. Treatment needs follow-up labs, including a blood count (to check hematocrit) and, depending on your age, PSA.
- The underlying cause. Sometimes improving sleep, losing weight or changing a medication raises levels on its own.
The bottom line
One low number is a reason to look closer, not a diagnosis. Repeat morning labs, a full symptom history and a look at the rest of your health give you a real answer.
Read more about how we evaluate low testosterone, or see what's in our baseline lab panel.