Testosterone levels are checked with a simple blood draw, typically from a vein in your arm, scheduled in the morning between 7 and 10 a.m. when levels naturally peak. The sample is sent to a lab, and results usually come back within a few days. While the process itself is straightforward, the details around timing, test type, and how to read your results matter more than most people expect.
Why the Blood Draw Happens in the Morning
Testosterone follows a daily rhythm, rising overnight and hitting its highest point in the early morning hours. By afternoon, levels can drop significantly. A blood draw between 7 and 10 a.m. captures your peak, giving the most reliable baseline. If you test later in the day, your results may look artificially low, potentially leading to an unnecessary diagnosis or repeat testing.
Most guidelines also recommend testing on two separate mornings before drawing any conclusions. Day-to-day variation is normal, so a single low reading doesn’t confirm a problem on its own.
Total Testosterone vs. Free Testosterone
Your doctor will almost always order a total testosterone test first. This measures everything in your blood: testosterone floating freely and testosterone bound to proteins, primarily a carrier molecule called sex hormone-binding globulin (SHBG). The total number gives a useful starting point, but it can’t tell you how much testosterone is actually available for your body to use.
That’s where free testosterone comes in. Only a small fraction of your testosterone circulates unbound, and that’s the portion your tissues can absorb. If your total testosterone comes back normal but you still have symptoms, or if the result lands in a borderline zone (roughly 200 to 400 ng/dL), your doctor may order a free testosterone test or measure your SHBG levels to get the fuller picture.
SHBG acts like a sponge. When SHBG is high, it soaks up more testosterone, leaving less free for your body. When it’s low, more testosterone is available. This is why two people with identical total testosterone numbers can feel very different. Conditions like obesity, liver disease, thyroid disorders, and aging all shift SHBG levels, which makes the free testosterone measurement especially important in those situations.
Do You Need to Fast?
This is a point of debate. Eating can suppress testosterone levels temporarily, and some expert guidelines recommend fasting before your draw for the most accurate result. However, at least one clinical study found no significant difference between fasting and non-fasting testosterone levels in practice. The median readings were nearly identical whether patients had eaten or not.
If your doctor asks you to fast, follow their instructions. If they don’t mention it, a morning draw at the right time is still the most important factor. Don’t skip your test just because you accidentally had breakfast.
How Labs Analyze Your Sample
Most commercial labs use a method called immunoassay, which is fast and inexpensive. It works well for levels in the normal range, but it has a known weakness: at low concentrations (below about 100 ng/dL), results become unreliable. One study found that immunoassay readings were 20% lower than the gold-standard method and showed minimal correlation with accurate measurements in that low range.
The gold standard is a technique called liquid chromatography-tandem mass spectrometry (LC-MS/MS). It provides accurate results across the entire measurable range, including the low values that matter most when diagnosing a deficiency. This method is also critical for testing women and children, whose levels are naturally much lower. If your results seem inconsistent with your symptoms, ask whether your lab used the more precise method.
What the Numbers Mean
The Endocrine Society defines the lower limit of normal total testosterone in healthy, non-obese young men as 264 ng/dL. Below that threshold, and with consistent symptoms, a diagnosis of testosterone deficiency (hypogonadism) is typically considered.
But “normal” shifts with age. A large study published through the American Urological Association found these average ranges for men in their 20s through 40s:
- Ages 20 to 24: middle range of 409 to 558 ng/dL
- Ages 25 to 29: 413 to 575 ng/dL
- Ages 30 to 34: 359 to 498 ng/dL
- Ages 35 to 39: 352 to 478 ng/dL
- Ages 40 to 44: 350 to 473 ng/dL
The gradual decline is real but modest. A 40-year-old with a level of 360 ng/dL is squarely in the normal range for his age, even though that same number would be on the low end for a 25-year-old.
Testing in Women
Testosterone testing isn’t just for men. In women, elevated testosterone is one of the key markers for conditions like polycystic ovary syndrome (PCOS). Symptoms that prompt testing include acne, excess facial or body hair, irregular periods, and thinning hair on the scalp.
The American College of Obstetricians and Gynecologists recommends measuring total testosterone, free testosterone, or both when evaluating these symptoms. A total testosterone level above 200 ng/dL in a woman raises concern for a hormone-producing tumor and typically triggers further imaging. Because women’s testosterone levels are so much lower than men’s, the accuracy limitations of standard immunoassays become even more relevant. The more precise mass spectrometry method is strongly preferred for female patients.
Medications That Can Skew Results
A long list of common medications can raise or lower your testosterone reading, independent of your actual hormonal health. Opioid painkillers are one of the most well-documented offenders, particularly with long-term use. Corticosteroids (like prednisone), certain anti-seizure drugs, the heart medication digoxin, the blood pressure drug spironolactone, and the antifungal ketoconazole can all suppress levels. On the other side, medications like finasteride (used for hair loss and prostate enlargement) and some anti-seizure drugs like valproic acid can push levels higher.
Let your doctor know about everything you take, including supplements, before your test. Context matters when interpreting results.
Are Home Test Kits Reliable?
Home testosterone kits, usually involving a finger prick or saliva sample, have become widely available. Their convenience is real, but their accuracy is a serious concern. In one study comparing six different home kits, results varied by 26 to 41% among men and 57 to 115% among women. When those home results were compared against an established clinical method, the average deviation was 194% in men.
Several factors drive this inconsistency. Home kits rely on the same immunoassay technology that struggles with low values. Users are also less likely to collect samples at the right time of day, in a fasted state, or handle samples properly before mailing them. A home kit might give you a rough sense of whether your levels are very high or very low, but it’s not reliable enough to base medical decisions on. A clinical blood draw analyzed with validated lab methods remains the standard for any diagnosis.
What Happens After an Abnormal Result
A single low result is never the end of the story. You’ll be asked to repeat the test on a different morning to confirm the finding. If the second result is also low, your doctor will likely order additional bloodwork, including free testosterone, SHBG, and hormones from the pituitary gland that regulate testosterone production. These follow-up tests help distinguish between a problem in the testes themselves and a signaling issue in the brain.
For women with elevated results, additional tests may include hormones related to adrenal gland function to rule out adrenal tumors or a genetic condition called non-classic congenital adrenal hyperplasia. Pelvic ultrasound is not routinely needed unless the testosterone level or degree of symptoms is high enough to suggest a tumor.