You're not overweight, so no one checked your blood sugar

You eat well. You move. You’re the size you have always been, and every appointment starts with someone glancing at you and deciding that whatever is going on, it isn’t that. So the blood sugar conversation never happens. Meanwhile your cycles are long, or unpredictable, or arriving without much happening in the middle of them. The ovulation tests are confusing. And the tiredness after lunch, the wired feeling at night, the way you get shaky if a meal is late.

Insulin resistance is not a body size

Insulin resistance is how well your cells listen to insulin. Slim women can be poor listeners while their blood sugar stays perfectly normal. That is the whole trick of it. Your pancreas simply makes more insulin to keep glucose where it should be, so the standard test comes back fine while the thing actually affecting your ovulation goes unmeasured. If you want it looked at properly, the marker to ask for is fasting insulin, measured at the same time as fasting glucose.

Insulin talks to the ovaries

Insulin doesn’t only manage blood sugar. When it runs high, it pushes the cells around the developing follicle to make more testosterone, and it works together with LH to amplify that effect.¹ A little testosterone is normal and necessary. Too much, at the wrong point in the cycle, can stop a follicle maturing and releasing the way it should. You might still bleed. Bleeding is not the same as ovulating.

This shows up in slim women more than most people expect. In research on women with PCOS (now called PMOS) at a normal weight, insulin resistance is still there compared with women of the same size and age without it, and when insulin is deliberately lowered in lean women, their ovarian androgens come down with it.² So the picture isn’t “extra weight causes this”. It’s that insulin affects ovulation whatever your size, and how strongly it’s doing that is not something anyone can tell by looking at you.

Glucose is a late signal

The other reason this gets missed is timing. Insulin sensitivity starts drifting long before glucose does. In one of the largest long-running studies following people towards a diabetes diagnosis, insulin sensitivity was already falling steeply while fasting glucose was still creeping up slowly and quietly within range.³ Fasting glucose is a late signal. If you’re waiting for it to move before anyone takes an interest, you’re waiting years, and if you’re trying to conceive now, those are not spare years.

The panel worth asking for

Fasting insulin, with fasting glucose, taken together as HOMA-IR, which is just a small calculation that tells you how hard your body is working to hold that normal glucose. HbA1c, for the three-month average. Triglycerides and HDL cholesterol, because the ratio between them tends to shift early. SHBG, the protein that holds hormones in circulation, which often sits low when insulin is high. None of these are unusual. They are ordinary tests that simply weren’t run, because you didn’t look like someone who needed them.

Where the change actually comes from

This is the point where wellness content usually tells you to cut carbohydrates. That is rarely what I do. Most of what changes insulin in a woman who is already eating well is not the food list. It’s the shape of the day: protein at breakfast rather than at dinner only, what you eat alongside the carbohydrate rather than instead of it, whether you’re eating enough overall, how you’re sleeping, how much your nervous system has been running past its limits. Undereating and overtraining can push insulin and cycles around too, and a slim woman trying to conceive is often doing both, even when it looks like eating carefully and staying active.

How I’d work with you

This is also why I don’t start with a protocol. Two women with identical fasting insulin can need almost opposite things, because one is under-fuelled and exhausted and the other is eating plenty but grazing all day on stress and coffee. We start by working out which one you are, and what your body is actually asking for.

If you’ve been told you’re fine because you’re not overweight, and your cycles are still telling you something different, that gap is worth closing. Bring the question to your doctor and ask for the fuller panel. If you’d rather have someone go through the whole picture with you, cycle, symptoms, food, sleep and all, that’s the conversation I’m here for. The numbers won’t tell you everything. But they tell you more than your weight does.

References