The same dose hits different in the luteal phase.
The calculator reads your cycle phase alongside your dose, so the GLP-1 month finally makes sense.
Most GLP-1 guidance assumes a constant body. Yours is not. The luteal phase, the two weeks before your period, slows gastric emptying, raises water retention, and amplifies nausea on the same dose that felt fine in the follicular phase. The pattern is well-documented in the gastric physiology literature, and easy to feel: month three on a GLP-1 can feel like four different medications.
The calculator treats your cycle as an input, not a calendar. Give it the first day of your last period and it works out which phase you are in, then adjusts your resting burn and your protein for the month and tells you which adjustment it made. Resting metabolic rate rises in the luteal week; appetite often dips in the follicular one. If you would rather not say, it steps aside and says so rather than guessing.
If you take tirzepatide, Mounjaro or Zepbound, there is a contraception interaction worth knowing about and it is not a nutrition question. The Eli Lilly label is explicit that tirzepatide can reduce the absorption of oral contraceptives, particularly in the four weeks after starting and after every dose increase. Most prescribers have not been trained to raise it. We are raising it here.
Built around how this medication actually works.
Phase next to dose
Home-screen card shows phase + day count + GLP-1 phase-specific advice.
Where you are in the month
Start, end, bleeding level, and cycle-specific symptoms, cramps, cravings, mood, energy.
Fertility-aware messaging
Appetite and nausea both move with the phase, so the same dose can feel entirely different two weeks apart. Expect both rather than fighting either.
Contraception interactions
Tirzepatide can reduce oral contraceptive effectiveness. Four weeks of barrier protection after starting and after every dose change.
What the studies actually say.
Evidence-based summaries of the papers that informed every part of this page. Each article cites its sources.
Your cycle and your GLP-1: why month three feels like four different medications
Gastric emptying, appetite, and water retention shift across the menstrual cycle, and GLP-1s stack on top. A phase-by-phase guide.
GLP-1s and the pill: a warning women on Mounjaro and Zepbound need to read
Tirzepatide can reduce the effectiveness of oral contraceptives. The label is clear about it; the conversation often isn't. Here is what to know, what to switch to, and for how…
GLP-1s and PCOS: what the early evidence shows for women with insulin resistance
Polycystic ovary syndrome and GLP-1 weight loss interact in ways that are still being studied. Here is what the small but growing literature shows about cycles, fertility, and…
GLP-1s in perimenopause: why the same dose hits different
The years before menopause change body composition, insulin sensitivity, and how a GLP-1 feels. Here is what shifts, and the small adjustments that make the medication work with…
Microdosing a GLP-1 in perimenopause or menopause: what is known, and what is not
Low-dose tirzepatide and semaglutide are marketed hard to women in midlife. Here is what the evidence actually covers, what it does not, the risks that come from how people…
GLP-1s and pregnancy: the two-month wash-out you need to plan for
GLP-1s are not approved for use in pregnancy. The standard guidance is to stop the medication two months before trying to conceive. Here is the reasoning, the gap in the data, and…
GLP-1s and fertility: the 'Ozempic baby' surprise, and the contraception catch no one mentions
Women on GLP-1s are reporting unexpected pregnancies, sometimes after years of trying. The reason is real biology, and it comes with a contraception warning that too few are told.…
GLP-1s and menopause: why the drug still works, and what to protect
Menopause changes where you gain weight and how fast you lose muscle. New analyses show GLP-1s work just as well after menopause, if you protect muscle and bone. Here is how.
GLP-1s and libido: what happens to sex drive on Ozempic and Wegovy
Some women notice their sex drive changes on a GLP-1. The picture is mixed and mostly indirect. Here is what is really going on, and what helps, in plain language.
Cycle-aware GLP-1 tracking, so you stop blaming yourself for biology. Free, and no sign-up.
Built around how your body actually works on Ozempic, Wegovy, Mounjaro and Zepbound. It runs in your browser, there is nothing to install, and nothing you type is stored.
For the daily version of this, food, dose, symptoms and the trend, there is the Foodose app for iPhone.