Where Is the Best Place to Apply Testosterone Gel?

For most prescription testosterone gels, the upper arms and shoulders deliver the highest blood levels of testosterone compared with other commonly used sites. That is why product labels for the major gel brands direct you there first. But the story gets more interesting once you look at newer formulations designed for the armpits, off-label scrotal application, and the practical question of how to keep the gel from rubbing off on the people around you. Where you apply matters not just for how well the drug works, but for safety.

Upper Arms and Shoulders Come Out on Top

The two most widely prescribed testosterone gels in the United States have slightly different labeling. One brand (Testim) is approved only for the arms and shoulders, while the other (AndroGel) lists the abdomen, shoulders, and upper arms as acceptable sites.¹ Both labels, though, steer you toward the upper arms and shoulders as the primary choice, and the pharmacokinetic data explains why.

A study comparing 1.62% testosterone gel applied to the upper arms and shoulders versus the abdomen found that abdominal application produced roughly 30 to 40 percent lower bioavailability.² In practical terms, that means a substantial fraction of the testosterone you rub onto your belly never reaches your bloodstream. A separate trial looking at Testim applied to three body regions found that arm application produced the highest total testosterone levels, followed by the chest, with a third site trailing behind.³ The consistent theme across studies is that the upper arm and shoulder area absorbs these formulations more efficiently than the alternatives.

Why Skin Location Changes Absorption So Much

Your skin is not a uniform barrier. The outermost layer, the stratum corneum, varies in thickness, cell maturity, and moisture-loss characteristics depending on where it sits on your body. Research measuring these properties across sites found that thinner-skinned areas like the cheek and wrist had smaller, less mature skin cells and lost more water through the surface, all of which generally correspond to easier drug penetration.⁴ The abdomen, by contrast, tends to have a thicker barrier with more subcutaneous fat underneath, which partly explains why testosterone gel does not cross as efficiently there.

The upper arms and shoulders sit in a sweet spot: the skin is relatively thin and well-vascularized without being fragile or irritation-prone. Blood flow near the surface helps carry absorbed testosterone into general circulation quickly. Areas with more fat tend to act as a local reservoir, trapping the hormone rather than delivering it systemically. This is also why most gel labels tell you to apply to clean, dry, intact skin: moisture, open cuts, or residue from lotions can alter how the gel interacts with the skin surface.

The Armpit as an Application Site

If the upper arms work well, the armpits work even better on a per-area basis. A head-to-head pharmacokinetic study compared a 1% testosterone solution applied to the armpit versus the inner arm and found that armpit application produced about twice the bioavailability.⁵ The axillary skin is thin, warm, and somewhat occluded by the natural fold of the arm, all of which help testosterone cross the barrier more effectively.

A testosterone topical solution specifically designed for armpit application has been studied in a larger trial and showed good results: after about two months, roughly 85% of users maintained average testosterone levels in the normal range with once-daily application.⁶ This product is a solution rather than a traditional gel, and it is formulated specifically for axillary use. You would not want to apply a standard gel to the armpit without your prescriber’s guidance, because the dose calibration is different and the risk of transfer to clothing changes. But the armpit route is a legitimate, FDA-cleared option that some men find more convenient than smearing gel across their shoulders.

Scrotal Application and the DHT Question

Scrotal skin is dramatically thinner than skin elsewhere on the body, and it has long been known to absorb steroid hormones with unusual efficiency. A pharmacokinetic study of testosterone cream applied to the scrotum confirmed this: even a much lower dose than what is used on conventional sites produced a swift rise in blood testosterone, peaking within about two to three hours and maintaining physiological levels for around 16 hours at a 25-milligram dose.⁷ That is a fraction of the 50 to 100 milligrams typically applied to the arms or shoulders.

The catch with scrotal application is what happens to dihydrotestosterone, or DHT. The scrotum contains a high concentration of the enzyme that converts testosterone to DHT, so scrotal application tends to push DHT levels higher than other routes do. In the same study, DHT concentrations rose in a time-dependent pattern, peaking a couple of hours after the testosterone peak.⁷ Whether elevated DHT is beneficial or harmful in a given individual is debated among endocrinologists. DHT plays roles in libido, mood, and certain tissue growth, but high levels have been linked to prostate concerns and hair loss in susceptible men. Scrotal application is not FDA-approved for standard testosterone gels, and prescribers who recommend it are working off-label. If your doctor suggests this route, the DHT issue is worth discussing explicitly.

Preventing Transfer to Other People

Secondary transfer is the biggest safety concern with topical testosterone. If someone else touches the area where you applied the gel before it has fully absorbed, they can pick up enough hormone to shift their own levels. This is especially concerning for female partners and children. A controlled study measured testosterone levels in women who had direct abdominal skin contact with a man who had applied 1.62% gel, and found that their testosterone concentrations rose 86 to 185 percent above baseline.⁸ That increase stayed within the normal female range in this study, and levels returned to baseline within 48 hours after the last contact, but repeated daily exposure could push things further.

Clothing makes a real difference, but how much depends on the application site. A t-shirt barrier cut testosterone transfer by about 40 to 48 percent when the gel was applied to the abdomen alone. When the gel was applied to the upper arms and shoulders, the t-shirt essentially eliminated transfer entirely, with only a 5 to 11 percent bump observed.⁸ This makes intuitive sense: a shirt covers the upper arms and shoulders snugly, trapping the gel against your skin and away from other people, whereas abdominal skin is more likely to be exposed during casual contact. Research comparing patches and gels reinforced this point, concluding that gel application sites should be covered with clothing to reduce the chance of skin-to-skin transfer.⁹

Interestingly, one older study found that after intense forearm skin contact between a treated man and untreated men whose own testosterone production had been suppressed, no measurable increase in the untreated men’s levels was detected.¹⁰ That study concluded that meaningful contamination through casual contact is unlikely. The discrepancy with the other findings probably reflects differences in how long after application the contact occurred, how much gel was used, and how prolonged the skin-to-skin exposure was. The safest approach remains the standard advice: cover the site, wash your hands after applying, and wash the application area before any close physical contact.

How Clothing Absorbs the Dose

Covering the application site protects others, but the fabric itself absorbs some of the testosterone you applied. A study of men using a 2% testosterone solution on the armpits found that unworn, unwashed t-shirts collected an average of about 13 percent of the applied dose. After a standard laundering cycle, the residual testosterone dropped to roughly 3 percent.¹¹ The variability between individuals was large, with some shirts retaining much more than others. This means the clothing barrier is not free: you lose a portion of your dose to fabric. It also means that sharing unwashed clothes with a partner or child could theoretically expose them to residual hormone, though laundering reduces the risk substantially.

Transfer dynamics also differ by where the gel sits on your body. When researchers measured testosterone transfer from upper-arm and shoulder application versus abdominal application, they found that direct skin-to-skin transfer was actually higher from the upper arms and shoulders.¹² That sounds paradoxical given that the same site is better protected by clothing, but it underscores the point: without a shirt in the way, the arms and shoulders are more likely to make direct contact with another person than the abdomen is. The clothing barrier, not the site itself, is doing the protective work.

When to Shower After Applying

Timing your shower wrong can wipe out a significant portion of the dose. A controlled study found that showering 15 minutes after applying testosterone gel slashed average plasma testosterone to unacceptably low levels, and showering at 30 minutes still produced significantly reduced concentrations compared to no shower.¹³ Most prescribing information recommends waiting at least two hours, but longer is better from an absorption standpoint.

Separate research on skin washing at various intervals after gel application found that washing the site at two or six hours reduced overall testosterone exposure by about 10 to 14 percent, while washing at 10 hours had no measurable effect on blood levels. Washing removed at least 81 percent of the testosterone still sitting on the skin surface, so the question is really how much has already crossed into your bloodstream before you wash. By 10 hours, most of the absorption has occurred and washing is essentially cosmetic. If you need to shower sooner, the two-hour mark appears to be the minimum for preserving most of the dose, though you will still lose a fraction compared with leaving the site undisturbed longer.

Skin Irritation and Whether You Need to Rotate Sites

Testosterone gels are generally gentle on the skin, especially compared with older transdermal patches. A trial evaluating gel application found no skin irritation in any of the subjects, even when the same sites were used repeatedly. The researchers concluded that the hydroalcoholic gel base dried in under five minutes and left no residue.¹⁴ This contrasts sharply with patch systems, where one trial found that about a third of subjects developed moderately intense redness at patch sites.¹⁵

Because gel irritation is so uncommon, strict site rotation is less important than it is for patches. Some prescribing labels still suggest alternating between left and right arms, but the evidence suggests this is precautionary rather than strictly necessary. If you do notice redness, dryness, or itching at a particular spot, switching to the other arm or a different approved site for a few days is a reasonable approach. Applying gel over broken skin, sunburned areas, or freshly shaved skin should be avoided, since damaged skin may absorb unpredictably and could sting from the alcohol content.

How the Gel Formula Itself Affects Absorption

Not all testosterone gels are created equal, and differences in the inactive ingredients can change how well the drug crosses your skin. The gels use alcohol-based vehicles that evaporate quickly, driving testosterone into the outer skin layers. Research into additional penetration enhancers has shown that certain excipients can substantially boost transport: one study found that a compound called isopropyl myristate increased testosterone penetration through skin by more than fivefold.¹⁶ A separate study examining another alcohol-based enhancer (isopropyl alcohol) in hydroalcoholic gels found that while it showed a trend toward improving testosterone release, the effect was not statistically significant compared with the standard formulation.¹⁷

What this means for you as a patient is that switching between brand-name and generic products, or between different concentrations (1% versus 1.62%), is not necessarily a one-to-one swap. The absorption profile can change with the formulation, and your testosterone levels may shift even if the labeled dose appears the same. If your prescriber switches your product, follow-up blood work a few weeks later is the only reliable way to know whether your levels are still on target. The application site recommendation may also differ between products, since formulations optimized for axillary use have different concentrations and vehicles than those designed for the arms.

Practical Tips That the Studies Support

Putting this all together, a few practical principles emerge from the research:

Apply to clean, dry skin: Residue from lotions, sunscreen, or sweat can interfere with absorption. Towel off after a shower and let the skin dry before applying.
Stick with the labeled site for your product: Upper arms and shoulders work well for most gels. If you are using an axillary formulation, apply only to the armpits.
Cover the site with a shirt: Clothing nearly eliminates the risk of secondary transfer from the upper arms and shoulders, while also keeping the gel layer undisturbed.
Wait at least two hours before showering: Longer is better. At ten hours, washing has no meaningful effect on absorption.
Wash your hands immediately: Your palms absorb testosterone poorly but transfer it efficiently to anything you touch.
Launder clothes before others wear them: Standard washing removes the vast majority of residual testosterone from fabric, but unwashed shirts can hold a meaningful amount.

If your blood levels are not reaching the target range despite consistent daily use, the application site is one of the first things worth revisiting with your prescriber. Switching from the abdomen to the upper arms, or discussing a product formulated for axillary use, can meaningfully change the amount of testosterone that actually reaches your bloodstream without increasing the prescribed dose.