Time of day
There's some justification for the premise that we should take our hormones once a day, in the morning. Our innate hormonal cycle (called diurnal or circadian rhythm), of ovarian and many other hormones, is to have circulating levels rise to their highest in the morning, and then gradually drop to the lowest during the night. Because a number of other hormones (such as melatonin, growth hormone, and thyroid hormone) are affected by this cycle, it thus would seem to make sense to follow this pattern with our HRT. Among other things, women with very low estrogen levels have trouble sleeping and their circadian rhythms are disturbed, which tends to reinforce the validity of this dosing scheme. This would also explain why hot flashes tend to break through more at night, when our levels are at their lowest, than during the daytime for many women.
This can be a little scary, though, when we read the literature that comes with our pills that talks about a lifespan of only hours before hormones are eliminated from the body. But in practice, some of our hormone dose ends up converted to less active forms and cached in our body fat, released slowly over time. This seems to compensate for the short life "in action" of the hormone for most women taking adequate dose quantities.
However much this may seem optimal, it doesn't always work. Some women find that their dose of progesterone, especially when taken orally, makes them too drowsy to want to take it during the day. For them, a nighttime progesterone dose seems to work better. Only very rarely is taking estrogen at night preferable, since its stimulating effects tend to prevent sound sleep as well as disrupting our normal daily hormone rhythms. The exception to that is the occasional woman whose doctor insists that she only use oral hormones of a specific dose but she's having nausea with them (a sign that she might do better with another route and/or a lower dose). In this case, taking them at night may let you sleep through the nausea…while you're shopping for a more responsive doctor.
The other question that frequently comes up is whether or not you need to worry about cycling your hormones on a monthly basis. This has its foundation in birth control pills, in which manufacturers add and subtract progesterone to the estrogen pills to allow for a monthly period. So too do women in natural menopause need to cycle progesterone to prevent endometrial cancer due to unopposed estrogen.
While this cycling was historically set up on a monthly basis in the belief that women would find it reassuringly like their own cycles, in fact there is no physiological justification for this and many women today cycle birth control and menopausal hrts on a quarterly basis or only as needed by measurements of endometrial thickness.
But once you don't have a uterus, that particular need is gone. In fact, the vast majority of women in surgical menopause (who have had a hysterectomy) feel better on a steady dose of hormones, taking estrogen and progesterone at the same dose every day of the month. Women who had surgery for endometriosis particularly need a steady dosing schedule to dampen out their endo, rather than cycling stimulation (with unopposed estrogen) of it. If you are in surgical menopause but still have a uterus, then you do need to cycle although it may not be required more than a few times a year.
For a short time after a hysterectomy and oophorectomy, you may feel as though you are still cycling. You get those mid-cycle feelings and wonder just how that can happen with the equipment gone. We've not found a credible explanation of the physiology behind this, but it does indeed happen. The best we can do is speculate that the body has a certain residual "habit" of cycling that takes a few month to run down. We've not heard of it persisting more than a few months in women without ovaries.
Some women have suggested that since it was "natural" for them to cycle every month, that cycle needs to be preserved. There is in fact no physiological basis for this. Cycling is only necessary for fertility and uterine recovery therefrom; in other ways, it's costly and detrimental to the body. It's the price we pay for reproduction, but one of the joys of menopause is being freed of the physical burden of reproduction.
Still, if you feel that you are not ready to relinquish the fertile life stage you left with your hyst, by all means set your HRTs up to whatever schedule of cycling seems required for your emotional comfort. It's all about how you weigh the different concerns, and if that's foremost on your list, go for it.
Despite this lack of physiological necessity, there are some doctors and pharmacists who are so unthinkingly attuned to the dangers of uncycled estrogen that they will not give non-cycling hormones to their patients even when they no longer have a uterus. On their doctors' orders, these women go on struggling, month after month, with the miseries of periodic unopposed estrogen, withdrawal of progesterone, and the joys of artificial PMS.
It's not necessary. Your body needs all of your hormones every day when you're on a minimal menopausal dose, and you are entitled to a dosing schedule that provides them. Even when we cycled naturally during our fertile years, we never went entirely without one of our hormones: both estrogen and progesterone rose and fell through the month but never bottomed out. So if your doctor prescribes you an HRT form that comes in a cycle-based package, go ahead and question it right away, before you reach the end and wonder what to do next. We in surgical meno are the oddities in most medical practices, and the unthinking habits of practitioners often mean they hand these out without considering our special needs. It's up to us to make sure that everything we take makes sense and reflects our own needs and desires. So question, and if you don't like the answer, question some more.
Other timing concerns
Each HRT works at its own cycle of rising and falling doses in the body. Sometimes these can present other problems for us when these cycles don't entirely suit our body's use of the hormones they contain. Since these are peculiar to each form of HRT, we'll take more of them up in the specialized discussions on specific HRTs.