Vitamin Deficiencies That Cause Fatigue in Women: A Complete Guide

The most common vitamin deficiencies causing fatigue in women include Iron (Anemia), Vitamin B12, and Vitamin D. Other critical nutrients like Folate (B9), Magnesium, and Vitamin C also play vital roles in energy metabolism. If you feel 'constantly tired,' these deficiencies often prevent your body from producing ATP or transporting oxygen efficiently.

In some cases, underlying medical conditions such as obstructive sleep apnea may contribute to persistent fatigue and require medical evaluation. Nutrient deficiencies can impair ATP production and oxygen transport, leading to persistent and unexplained fatigue.

Fatigue in women is often ignored due to hectic schedules and daily responsibilities. However, women are susceptible to several factors, including menstruation, pregnancy, hormone variations, eating habits, and indoor life.

Maintaining a healthy weight also plays an important role in sustaining energy levels. Persistent fatigue should not be ignored, as it may indicate underlying health conditions that require timely diagnosis and treatment.

A balanced, healthy diet is crucial in reducing fatigue. Dietary changes, such as adopting a balanced diet rich in essential nutrients, can help address nutrient deficiencies and support energy levels. It is recommended to discuss a treatment plan with your healthcare provider.

Here, we will discuss a detailed, science-based analysis of the most common trio of deficiencies that cause fatigue in women (Iron, Vitamin B12, and Vitamin D). Also, you will know how to effectively identify, diagnose, and treat them without risk, including the importance of a blood test to detect deficiencies and underlying conditions.

When women feel constantly exhausted, sleep deprivation or a hectic lifestyle can be the reason behind it. Energy production relies on an exact balance of micronutrients. Consuming certain foods rich in essential nutrients, certain vitamins, and minerals is crucial.

Even mild nutrient deficiencies can disrupt metabolic balance long before an underlying disease becomes clinically evident. Iron, vitamin B12, and vitamin D are among the most clinically significant nutrients with a direct and measurable impact on energy levels, stamina, neurological function, and sleep quality.

Iron is a vital mineral as it helps to make haemoglobin, which is the protein in red blood cells. It transports oxygen present in the lungs to all tissues in the body. In low iron medical conditions, the amount of oxygen is reduced. Consequently, the cells fail to generate energy and make you feel exhausted.

Iron deficiency exists on a spectrum:

• Iron depletion (low ferritin, normal haemoglobin)

• Iron-deficiency anaemia (low level of ferritin + low haemoglobin)

Even a lack of iron at an early stage, when anaemia is not yet developed, may result in great fatigue. Consuming iron-rich foods helps to promote healthy red blood cells and improve energy.

Women are disproportionately affected due to:

• Menstrual blood loss (heavy/prolonged period)

• Pregnancy and breastfeeding (increased iron needs)

• Postpartum depletion

• Low bioavailable iron diets (vegetarian/vegan patterns)

• Disorders such as fibroids, PCOS, or endometriosis

Iron deficiency is the most prevalent nutritional deficiency in all women of reproductive age in the world.

Fatigue from iron deficiency is often described as:

• Continuous fatigue despite sleep

• Pale skin or inner eyelids

• Cold hands and feet

• Shortness of breath during mild exertion

• Dizziness or headaches

• Thinning hair and brittle nails

• Restless legs, especially at night

Important note: Fatigue can continue weeks to months before the onset of anaemia on a routine blood count, which explains the importance of the ferritin test. If you experience unexplained fatigue, routine blood work and a blood test are important to help identify underlying vitamin deficiencies or other causes.

Vitamin B12 (cobalamin) is essential in:

• Red blood cell production

• DNA synthesis

• Myelin (nerve insulation) formation.

• Brain energy metabolism

Lack of sufficient B12 prevents cells from dividing effectively and nerves from transmitting signals effectively. It causes mental exhaustion and an inability to manage stress. You should consult a healthcare professional to develop strategies that support overall health and immune function.

Women at higher risk include:

• Vegetarian and vegan diets (B12 is found in animal products)

• Autoimmune disease

• Pregnancy

• Individuals with thyroid disease or autoimmune disease

• Specific medications

• Gut disorders (IBS, celiac, gastritis).

B12 deficiency may also be experienced despite sufficient nutrient intake because of the absence of absorption.

Common symptoms of fatigue caused by vitamin B12 include:

• Deep, persistent tiredness

• Loss of concentration and brain fog

• Dry skin

• Vision loss

• Memory issues

• Pain or numbness in the hands and feet

• Muscle weakness or heaviness

• Change of mood (low mood, irritability)

• Glossitis (smooth and sore tongue)

Deficiency in vitamin D impairs muscle contraction, mitochondrial production of energy, and the balance of neurotransmitters. It directly causes fatigue.

• Brain tissue

• Skeletal muscles

• Immune cells

• Mitochondria (energy powerhouses)

• Limited sun exposure

• Air pollution

• Poor diet

• Excessive caffeine intake

• Sleep issues

• Vegan and vegetarian diet

• Malabsorption Issues

• Obesity

• Pregnancy and breastfeeding.

Vitamin D–related fatigue often feels different:

• Constant low energy

• Muscle aches or bone pain

• Heaviness in arms and legs

• Frequent infections

• Loss of mood or depressed mood

• Poor sleep quality

• Back pain

Fatigue is not created in equal measure for every woman. Lifestyle-induced fatigue, which may be a result of late nights, temporary stress or overwork, tends to improve with rest and a change of routine. Incorporating regular exercise, high-quality sleep, and enough sleep can help reduce stress and improve fatigue.

Fatigue caused by vitamin or mineral deficiencies does not subside easily and often worsens over time if left untreated. It increases with age and often has physical symptoms. Vitamin and mineral deficiencies that cause fatigue are usually characterized in the following ways:

Fatigue associated with the lack of vitamins and nutrients is not intermittent. It is there on most days. As long as a nutrient deficiency persists in the body, fatigue is likely to continue.

You can even be exhausted, heavy or mentally clouded after 7-9 hours of sleep, especially if disruptions in the sleep cycle, sleep disturbances, or difficulty staying asleep are present.

Naps do not help much, as the lack of sleep is not an issue, but the energy level of cells. Until the nutrient deficiency is corrected, fatigue is likely to persist.

Nutrient deficiency fatigue does not necessarily improve quickly. It may deteriorate within a few weeks or months. In some cases, chronic psychological stress can lead to stress-related exhaustion disorder, a condition characterized by persistent physical and mental fatigue.

Most of the women get used to it, thinking it is normal, until tasks begin to stress them every day, highlighting the importance of strategies to reduce stress, such as relaxation techniques and self-care.

Fatigue rarely occurs as an isolated symptom. The typical co-morbid conditions are:

• Thinning or excessive hair fall

• Pain or numbness in the hands and feet

• Pain in the muscles, joints or bones

• Pallor, dark circles, and crumbling nails

• Loss of clarity, lack of concentration, or mood alteration

These symptoms indicate that the body is trying to carry out activities without nutrients to carry out the functions of oxygen delivery, nerve signalling, and muscle performance.

An easy clinical rule to aid in determining when it is necessary to test is the Rule of 3. You are advised to seriously consider a medical assessment when you feel fatigue:

• Lasts more than 3 weeks: Sometimes it can happen with short-term fatigue, as chronic fatigue is not usual. After a period of three weeks, one should consider the nutritional causes.

• Consistent even with sufficient sleep and rest: When sleep, hydration and low workload fail to enhance the level of energy, then it is probably a biochemical problem and not behavioural.

• Disturbs normal functioning: The red flags are difficulty in accomplishing routine tasks, low work performance, lack of motivation, or avoidance of social activities.

At this point, it is necessary to test. Symptom guessing, self-supplementing, or ignoring may delay treatment and aggravate deficiencies.

The specified diagnosis methodology can be used to pinpoint the precise cause of fatigue, including identifying any underlying medical condition, and prevent excessive supplementation. In cases of reduced vitamin levels, vitamin supplements may be recommended to help restore healthy levels. The most effective fatigue workup of a woman relies on the following tests:

It is the initial screening test of fatigue. It evaluates:

• Hematocrit (oxygen-carrying capacity) and haemoglobin.

• Red blood cell size and count

CBC is useful for diagnosing anaemia. However, it may seem normal in an initial iron or B12 deficiency. It should not be used alone to rule out nutritional causes of fatigue.

Ferritin represents the availability of iron in the body and is the most vulnerable indicator of iron deficiency at an initial stage.

• Even normal haemoglobin can result in fatigue due to the low level of ferritin

• Symptoms manifest in many women when the level of ferritin drops below the optimal levels, which are not limited to laboratory-defined normal levels

The test is essential among menstruating women and also heavy bleeders.

Measures required to circulate B12:

• Red blood cell formation

• Nerve function

• Brain energy metabolism

Before anaemia ensues, low or borderline levels of B12 may result in fatigue, brain fog and neurological symptoms. In other instances, other markers might be required when the symptoms are high, yet the levels are at the borderline.

This is the gold standard test of the vitamin D status.

• Indicates the amount of vitamin D in the body

• Very closely associated with muscle strength, mood, immunity, and energy

Even in sunny areas, deficiency is widespread and is often ignored as a factor of fatigue.

Doctors can prescribe further investigations depending on symptoms and history:

• Folate (Vitamin B9): Critical in the DNA synthesis and the manufacture of red blood cells, particularly during pregnancy and reproductive-age women. People with kidney disease may be at higher risk for folate deficiency.

• Thyroid-Stimulating Hormone (TSH): Helps eliminate hypothyroidism, which is a frequent form of fatigue and usually coincides with iron and B12 deficiency. Thyroid disorders can cause both weight loss and weight gain, and these weight changes are often linked to other symptoms such as hair loss and changes in energy levels.

• CRP (C-reactive Protein): A marker of inflammation. Prolonged inflammation has the potential to reduce the absorption of nutrients and lead to persistent fatigue.

Most of the symptoms of fatigue are similar to deficits, thyroid diseases, and inflammatory diseases. Without testing:

• Deficiencies may be missed

• Symptoms may be covered by inappropriate supplementation

• Root causes are still unaddressed

Systematic diagnosis routes will be able to treat the fatigue at its origin and treat it more accurately and quickly. It helps to restore energy, concentration, and physical prowess.

At MyDiagnostics, you can find the complex Women's Health Fatigue Panels that provide an assessment of iron status, vitamin B12, vitamin D and other such relevant markers, from the comfort of your residence. 

These panels are meant to decipher the latent shortcomings before they advance into chronic fatigue or a persistent complication.

Fatigue is not a personal failing, nor is it always the result of stress or lifestyle choices. For many women, it is a biological signal of nutrient depletion. Iron, vitamin B12, and vitamin D are the basis of cellular energy production, oxygen supply and neural activity.

Recognising and correcting these deficiencies can be life-altering, restoring clarity, strength, and long-term vitality. The point is early diagnosing, focused correction, and regular control of energy is not a choice; it is a necessity.