Iron and fatigue: why hemoglobin is normal but you have no energy
One in three women who menstruate lives with iron deficiency despite normal hemoglobin. Ferritin, symptoms, food, and when supplements are needed.
Insulin, Thyroid and Weight
Insulin is a hormone that decides where what you eat will go: to work or into storage. As long as cells hear it well, weight stays stable without effort. When they stop hearing it, that is insulin resistance, and then “I eat little, but my weight won’t budge” becomes the truth, not an excuse. In women, the thyroid gland, PCOS, and iron are added to this: three reasons why fatigue and extra pounds persist even though nutrition is already in order. This section is about how to recognize them through tests and what the method does about them. The main page on the topic is women’s health and the method.
8-13%
women live with PCOS
below 30
µg/L ferritin — iron deficiency
5-8×
hypothyroidism is more common in women
2,7
HOMA-IR — threshold for concern
How Insulin Controls Weight
Every meal containing carbohydrates raises blood sugar; insulin removes it and at the same time prevents fat cells from releasing fat. While insulin is high, fat is not burned. If you have six snacks a day, insulin is high almost all the time, and the body lives in storage mode. Over time, cells dampen the signal, more insulin is needed, and hunger and cravings for sweets grow. It is a vicious cycle, and it can be broken from two sides: eliminate frequent blood sugar spikes and restore periods without food. This is exactly what a low-carbohydrate diet and a fasting window in the method do — learn more in the article insulin resistance in women.
Which tests show this
| Indicator | Range | What exceeding it means | What to do |
|---|---|---|---|
| Fasting insulin | 2-10 µU/mL | above 10 — cells already respond poorly to insulin | low-carbohydrate diet, 14/10-16/8 window |
| HOMA-IR | up to 2.7 | above — insulin resistance | same plus strength training 2-3 times a week |
| Glycated hemoglobin | up to 5.7% | 5.7-6.4 — prediabetes | doctor, diet, check-up in 3 months |
| TSH | 0.4-4.0 mU/L | above 4 — hypothyroidism is possible | endocrinologist; gentler fasting |
| Ferritin | 30-100 µg/L | below 30 — iron deficiency | red meat, liver; find the cause with a doctor |
PCOS: why the method works especially well here
Polycystic ovary syndrome is the most common hormonal disorder in women, and in most cases it is driven by insulin resistance. High insulin levels cause the ovaries to produce more androgens, leading to cycle irregularities, breakouts, unwanted hair growth, and weight that refuses to budge. Reducing carbohydrates and using a fasting window target the root cause directly: insulin drops, androgens follow, and the cycle often returns even before there is a noticeable change in weight. What exactly to eat and which mistakes are most common are covered in the article PCOS and low-carb eating.
Thyroid gland: when to make fasting less strict
Hypothyroidism slows metabolism, and on it, weight increases on the same foods that used to keep you in shape. Here, it is important not to confuse the order: first, tests and treatment with an endocrinologist, then nutrition. The method is not canceled in hypothyroidism, but the fasting window is shorter, calorie intake is not below the recommended level, and iodine, selenium, and protein are on the plate every day. Long fasts and a strict calorie deficit with a diseased thyroid have the opposite effect — TSH rises. Read the analysis in the article thyroid gland and weight.
Iron: fatigue mistaken for laziness
One in three women with a regular menstrual cycle loses more iron than she gets. Hemoglobin may still be normal — ferritin, the body’s iron stores, falls. Symptoms include drowsiness, shortness of breath when climbing stairs, hair loss, icy hands, and a craving for ice. With low ferritin, workouts don’t go well, and fasting is harder to tolerate. In this approach, iron comes from food: red meat, liver, and seafood — and this is one of the reasons why a woman’s plate differs from a man’s. How to read your test results and when supplements are needed — in the article iron and fatigue.
Section Rules
Tests before conclusions
Insulin, HOMA-IR, TSH, ferritin — four figures that explain “the weight won’t budge” more often than lack of willpower.
Periods without food matter more than calories
Snacks keep insulin high. Three meals and a fasting window lower it without counting.
Thyroid — treatment first
Nutrition helps, but does not replace hormones. With TSH above 4 — see an endocrinologist before experimenting with a fasting window.
Iron from the plate
Red meat and liver once a week — the minimum for a woman with a menstrual cycle. Ferritin below 30 — find the cause.
Common mistakes
- Judging insulin resistance by weight rather than by a test
- Starting prolonged fasts with untreated hypothyroidism
- Taking iron “just in case” without checking ferritin
- Cutting out carbohydrates while simultaneously reducing calories to 1000
- Expecting rapid weight loss with PCOS—the menstrual cycle returns first, and weight follows later
Frequently Asked Questions
Can I fast with insulin resistance?
Yes, a 14/10-16/8 window is one of the most direct ways to lower insulin. Start with a short window and monitor how you feel; if you take glucose-lowering medications, do so only with a doctor.
Is this method allowed with hypothyroidism?
Yes, when hormone levels are controlled. Keep the window shorter, do not lower calories below the recommended amount, and have protein and selenium every day. Fasting for longer than 16 hours — no.
How long will it take to see results with PCOS?
The cycle often becomes more regular within 2-3 months of a low-carbohydrate diet. Weight loss is slower than in women without PCOS, and that is normal.
My hemoglobin is normal — does that mean I have enough iron?
No. Hemoglobin drops last. The reserves go first — ferritin. Ask for that specific test in your lab work.
Articles in this section
Thyroid and weight: when it’s not about food
Hypothyroidism slows metabolism, and weight increases on the same diet. Which tests to take, at what levels to ease fasting, and how the method works with thyroid disease.
Insulin resistance in women: signs, tests, and what to do
Weight won’t budge, you crave sweets, and after eating you feel sleepy — this is what insulin resistance looks like. Which tests to take, what the normal ranges are, and how the method helps reverse it.
PCOS and low-carb eating: what really works
Insulin is at the root of most cases of PCOS. Why low-carb eating restores the cycle sooner than weight is lost, and what mistakes are made most often.
Reviewed by Anastasia Zhukova, Fitness Trainer • Author of a Nutrition and Training System • Creator of an AI Personal Support Platform
A human has reviewed this material against the method and real client practice.