Original of this article was published on ZRT Laboratory Blog. Last reviewed: May 2026.
Over 25 million women a year worldwide will enter menopause and make a decision about hormone replacement therapy. For healthcare practitioners, what dosage and what formulation these hormones take is open to debate.
After many years of teaching and talking to practitioners, I’ve learned that: there are many strategies for approaching dosages, everyone thinks that theirs is the best, most of them work well for many patients but not all, and that we really, really need more research.
The Research Gap in HRT Dosing
There is very little to no research on different dosing strategies. Standard bioidentical hormones have research behind them, but they are looking at serum testing and usually compare themselves to placebos rather than each other. When you look at the doses of some of these products, you can see the large variation all used to treat the same condition.
For instance, in estrogens we have estradiol patches which dose from 0.025mg to 0.1mg a day. At the same time we have Estrasorb™ 4.35mg/packet with 2 packets, commonly used for a total of 8.625mg per day. There is also compounded supplementation at dosages as low as the patches, to one protocol that doses hormones at twice the dose of Estrasorb™ (16mg daily).
How can all of these doses be for the same symptoms? How can they all have the same side effects? How can the manufacturers come up with these doses and why are they so different from each other? The answer lies in the testing methods and the delivery pharmacodynamics.
Why Testing Method Matters
If you only test in serum, you will tend to overdose your topical creams. But, because serum tests have been used for most of the research on hormone replacement therapy, you find that most topical creams cite absorption rates of only around 10%, which is frankly, a pretty poor product if it were true.
At ZRT, we believe that absorption rates of most topical creams are closer to 90% or above. However, when you dose topical creams, the delivery is not a steady state delivery, but is instead a “bolus” effect. Topical creams seem to absorb very quickly and release their hormones very quickly. Saliva and blood spot testing catches these levels rather than showing the baseline levels or barely elevated values seen in serum.
For women on or considering HRT, our Comprehensive Female Saliva Hormone Profile (LCMS) measures estradiol, progesterone, testosterone, DHEA-S and cortisol from a simple at-home saliva sample — capturing the bolus effect of topical hormone delivery that serum testing misses.
The Need for Better Research on Topical Hormone Delivery
We know that serum, saliva, blood spot and urine can all tell us different things because we test in all these mediums. But no one is really looking at how these hormones are passing into the different mediums through the body.
When we compound hormones, we introduce dosages, topical formulations of creams and troches and combinations that have not been well studied. We need to look at not only our dosages, but also the pharmacodynamics of our delivery system, as well as the patient’s lab results in a helpful lab matrix to determine if we are getting the optimal results for our patient.
For women wanting a comprehensive baseline before or during HRT, our Advanced Female Wellness Test provides a thorough at-home hormone panel with a specialist doctor report included — covering the key markers needed to guide dosing decisions. If you prefer blood spot testing, our Female Saliva Hormone Profile II (LCMS) offers an expanded panel of sex hormones from a convenient at-home sample.