Constant fatigue: iron, ferritin, vitamin D

Constant fatigue: what causes does the doctor check first?

Fatigue: not a diagnosis, but a symptom. If you are constantly tired, your doctor will rule out various causes:

• Sleep disorders: sleep apnea syndrome (stopping breathing during sleep, often with snoring), insomnia, chronic lack of sleep
• Depression and Anxiety Disorders
• Hypothyroidism (low thyroid function)
• Anemia and iron deficiency
• Diabetes mellitus
• Side effects of medications
• Previous infections, diseases of the heart, lungs, kidneys, liver
• Pregnancy

Similar fatigue occurs with iron deficiency, sleep apnea syndrome and depression, and their treatment varies, so it is difficult to independently determine the cause. Below we talk about deficiency of iron, vitamin D and B12, which are often detected in women 30–55 years old, but this is only a part of the possible causes.

Why “normal hemoglobin” does not exclude iron deficiency

Hemoglobin: A protein in red blood cells that carries oxygen. Iron is required for its synthesis. Iron deficiency develops in stages:

1. Iron reserves are depleted: ferritin decreases, hemoglobin is normal
2. Not enough iron to produce new red blood cells, hemoglobin still within normal range
3. Iron deficiency anemia: hemoglobin decreases

The first two stages in the clinical guidelines of the Ministry of Health are called latent iron deficiency (reserves are depleted with normal hemoglobin concentration). A general blood test at this stage does not show any abnormalities, although the patient may be bothered by fatigue, hair loss and brittle nails.

The main causes of iron deficiency in women of childbearing age: heavy menstruation, pregnancy, childbirth (especially repeated ones) and breastfeeding.

Clinical practice guidelines describe two groups of presentations. Anemic syndrome: weakness, headache, dizziness, decreased exercise tolerance, decreased performance and concentration, pallor. Sideropenic syndrome (associated with a lack of iron in the tissues): dry skin, changes in nails, hair loss, angular cheilitis (seals in the corners of the mouth), burning of the tongue, perversion of taste. Sideropenic manifestations may appear before hemoglobin decreases.

What is ferritin and why is it evaluated along with inflammatory markers

Ferritin: A protein in which tissues store iron. Its level in the blood reflects iron stores, therefore, according to clinical recommendations, ferritin is tested in all patients with suspected iron deficiency.

Ferritin is also an acute phase protein: during inflammation and infection, including recent infections, its level increases and can mask a deficiency. Therefore, ferritin is assessed together with C-reactive protein (a marker of inflammation), if necessary with transferrin and the coefficient of transferrin iron saturation. The doctor interprets the result taking into account complaints and other indicators.

Does iron help with fatigue without anemia

According to randomized trials, in women with confirmed iron deficiency without anemia, correction of deficiency reduces subjective fatigue. Iron intake did not affect objective physical performance in these studies.

If iron stores are normal, iron supplements will not help and may cause harm (more on this below).

Vitamin D in St. Petersburg

The skin produces vitamin D when exposed to ultraviolet light, but only when the sun is high enough above the horizon. According to the clinical recommendations of the Russian Association of Endocrinologists, at latitudes above the 35th parallel from November to March, the synthesis of vitamin D in the skin is practically absent. St. Petersburg is located on the 60th parallel; cloudiness, closed clothing and sunscreen reduce synthesis.

According to Russian studies, vitamin D insufficiency and deficiency are detected in most adults, especially in late winter and spring.

Vitamin D and fatigue: what we know

Clinical guidelines associate vitamin D deficiency primarily with the musculoskeletal system: bone pain, muscle weakness, especially in the muscles of the hips and shoulder girdle. Fatigue as a separate manifestation of deficiency is not described in the recommendations. Randomized studies specifically focusing on fatigue are few, small and short-term.

Severe deficiencies are identified and corrected primarily for the sake of bones and muscles. Russian recommendations do not provide for mass screening and suggest determining vitamin D levels in risk groups: age over 60 years, obesity, intestinal diseases with malabsorption, chronic kidney disease and others.

B12: who should check

Vitamin B12 is essential for blood formation and nervous system function. According to the British NICE guidelines, unexplained fatigue is one of the symptoms for which a B12 test is warranted, especially if there are risk factors:

• Vegan or strictly restricted diet
• Long-term use of metformin (a drug to treat diabetes) or drugs that reduce stomach acid
• Autoimmune gastritis, gastric surgery, including bariatric surgery
• Other autoimmune diseases

If you are already taking a B12 complex, the test may show normal levels if tissue deficiency persists. Therefore, tell your doctor about taking supplements before scheduling a test. First analysis, then supplements.

Why it's dangerous to take iron and vitamin D "just in case"

The body does not have a mechanism for active removal of iron: excess is deposited in the liver, heart, and pancreas. In patients with hereditary hemochromatosis (a disorder in which excess iron is absorbed from the intestines), supplementation accelerates liver and heart damage, and diagnosis is often delayed. Iron supplements, even in normal doses, often cause side effects from the gastrointestinal tract: diarrhea or constipation, nausea, stomach discomfort.

Additionally, taking iron without a diagnosis may mask the cause of the deficiency. If she has occult bleeding or bowel disease, drugs will increase hemoglobin and delay diagnosis.

Excessive intake of vitamin D supplements can lead to hypercalcemia (increased blood calcium levels): nausea, vomiting, thirst, increased urination, kidney stones, muscle weakness. The synthesis of vitamin D in the skin does not lead to an overdose. According to Russian recommendations, hypercalcemia is rare, but the number of cases is growing, so calcium levels and 25(OH)D are monitored during treatment.

Iron and vitamin D preparations in therapeutic doses: medicines. The dose and duration of treatment are selected by the doctor based on test results, taking into account the initial level, body weight, concomitant diseases and tolerability.

What tests are usually discussed with your doctor?

The examination begins not with a test form, but with a question: quality of sleep, snoring, the nature of menstruation, medications taken, mood, past infections. The selection of studies depends on the responses. Most often discussed:

• Complete blood count: hemoglobin, erythrocyte indices (size and saturation of erythrocytes with hemoglobin)
• Ferritin together with C-reactive protein, if necessary transferrin and its saturation coefficient
• TSH (thyroid-stimulating hormone, which assesses thyroid function)
• Glucose or glycated hemoglobin
• Vitamin B12 for risk factors listed above
• 25(OH)D (the main form of vitamin D in the blood) for risk factors or if treatment doses are planned
• Other tests as indicated: liver and kidney function, gynecological examination for heavy menstruation

Reference values for ferritin and vitamin D vary depending on guidelines and laboratories, so your doctor will interpret the results.

When it's time to see a doctor

Make an appointment if fatigue persists for more than a month and does not go away with proper rest, if it is accompanied by hair loss, brittle nails, shortness of breath with normal activity, dizziness, heavy or frequent periods, or if you have been taking supplements for several months without noticeable difference.

Call your doctor urgently rather than routinely if you have unexplained weight loss, blood in your stools or black stools, fever, night sweats, chest pain, or shortness of breath at rest.

You can discuss the test results with your doctor at an appointment with a referral identification and correction of deficiencies, for a wider survey there is body check. In case of heavy menstruation, the examination begins with consultation with a gynaecologist: Until the source of iron loss is identified, replenishing the deficiency will not correct the cause.

Clinic servicesIdentifying and correcting deficiencies · Body check · Consultation with a gynaecologist