Iron Deficiency & Heavy Periods: What to Know

When Tired Isn't Just Tired

You wake up exhausted despite a full night's sleep. By 3pm you're barely functioning. Climbing a flight of stairs leaves you oddly breathless. You've blamed stress, poor sleep, a demanding schedule — but what if the real culprit has been bleeding out of you every single month?

Iron deficiency is one of the most common nutritional deficiencies in the world, and menstruating people are disproportionately affected. Yet the connection between heavy periods and chronically low iron is routinely missed — both by individuals managing their symptoms alone and, frustratingly, by healthcare providers who dismiss fatigue as simply "normal."

Here's what's actually happening in your body, and what you can do to restore your iron levels and reclaim your energy.

How Much Blood Is Too Much?

First, some grounding context. The average menstrual period involves losing between 30 and 40ml of blood — roughly two to three tablespoons. Heavy menstrual bleeding, clinically termed menorrhagia, is defined as losing more than 80ml per cycle, or bleeding heavily enough to significantly interfere with daily life.

In real terms, that might look like soaking through a pad or tampon every hour for several hours in a row, passing clots larger than a 50p coin, or bleeding for more than seven days. If any of that sounds familiar, you're not imagining it — and you're far from alone.

"Heavy menstrual bleeding affects approximately one in three women at some point in their reproductive lives, yet many suffer in silence for years before seeking help. The downstream consequences — particularly iron deficiency — are entirely preventable with appropriate assessment and support."
— Dr. Paula Hillard, MD, Professor of Obstetrics & Gynecology, Stanford University School of Medicine

According to the Centers for Disease Control and Prevention, heavy menstrual bleeding is one of the most common gynaecological complaints, affecting up to 10 million people in the United States each year.

Understanding Iron: Why You Need It So Badly

Iron is an essential mineral, and your body needs it for a surprisingly wide range of functions. Its most famous job is helping red blood cells carry oxygen around the body via haemoglobin — but it also plays a critical role in energy metabolism, immune function, cognitive performance, and the production of thyroid hormones.

When iron stores are depleted, every cell in your body feels it. The brain becomes foggy. Muscles tire quickly. The immune system becomes sluggish. Even your mood takes a hit, because iron is involved in the synthesis of dopamine and serotonin.

Iron deficiency exists on a spectrum:

• Iron depletion: Stored iron (ferritin) is low, but haemoglobin remains normal. Symptoms may be subtle or absent.
• Iron deficiency without anaemia: Tissue iron is low and symptoms become more noticeable, but haemoglobin is still within the normal range. This stage is frequently missed on standard blood panels.
• Iron deficiency anaemia: Haemoglobin drops below normal, and symptoms become significant — severe fatigue, pallor, breathlessness, heart palpitations.

Why Heavy Periods Deplete Iron So Fast

Each millilitre of blood contains approximately 0.5mg of iron. If you're losing 80ml or more per cycle, that's 40mg of iron or more — gone every month. The recommended daily intake for menstruating adults is just 18mg, and most people aren't absorbing anywhere near that from their diet. The maths, unfortunately, do not work in your favour.

This is why heavy menstrual bleeding is the leading cause of iron deficiency anaemia in premenopausal people worldwide. And the relationship runs in both directions: low iron can itself worsen menstrual bleeding, creating a frustrating cycle that's hard to break without addressing both ends.

Research published by the National Institute of Child Health and Human Development highlights that underlying conditions such as fibroids, endometriosis, adenomyosis, thyroid disorders, and bleeding disorders like von Willebrand disease are common drivers of heavy periods — which is why getting a proper diagnosis is so important rather than simply supplementing iron and hoping for the best.

Symptoms You Might Be Attributing to Something Else

Iron deficiency is a master of disguise. Many of its symptoms are so common in modern life that they're easily explained away. Watch for:

• Persistent fatigue that doesn't improve with rest
• Brain fog and difficulty concentrating
• Low mood, anxiety, or irritability
• Pale inner eyelids, lips, or gums
• Brittle nails or hair loss
• Cold hands and feet
• Unusual cravings for non-food items (ice, dirt, chalk) — known as pica
• Restless legs, particularly at night
• Frequent headaches
• Reduced exercise tolerance

"Iron deficiency without anaemia is enormously underdiagnosed. I see patients who have been told their bloods are 'normal' for years, yet their ferritin is sitting at 8 or 12. A ferritin below 30 is functionally deficient for most people — and optimal for energy and cognition is typically above 70."
— Dr. Jolene Brighten, NMD, Naturopathic Endocrinologist and Author of Is This Normal?

Getting Tested: What to Actually Ask For

A standard full blood count (FBC or CBC) will check haemoglobin, but this is a late-stage marker of iron deficiency. To catch the problem earlier — and to get a truer picture of your iron status — ask specifically for:

• Serum ferritin: Your iron storage protein. This is the most sensitive early marker of deficiency.
• Serum iron: The amount of iron circulating in your blood.
• Transferrin saturation: How well your iron-carrying protein is being utilised.
• Total iron-binding capacity (TIBC): An indirect measure of transferrin; rises when iron is low.

Note that ferritin is also an acute-phase reactant, meaning it can appear falsely elevated if you're fighting an infection or dealing with inflammation. Testing when you're well gives the most accurate result.

Rebuilding Iron Through Food

Diet is your first and most sustainable line of defence. Iron comes in two forms:

Haem iron (from animal sources) is the most bioavailable form — your body absorbs roughly 15–35% of it. Rich sources include:

• Beef, lamb, and dark poultry meat
• Liver and organ meats
• Oysters and clams
• Sardines and anchovies

Non-haem iron (from plant sources) has lower bioavailability — typically 2–20% absorption — but can be significantly improved with the right dietary strategies. Rich sources include:

• Lentils, chickpeas, and black beans
• Tofu and tempeh
• Pumpkin seeds and hemp seeds
• Dark leafy greens (spinach, Swiss chard)
• Fortified cereals and breads
• Dried apricots, figs, and prunes

Absorption Boosters and Blockers

What you eat with iron-rich foods matters enormously.

To increase absorption: Pair iron-rich foods with vitamin C sources — a squeeze of lemon over lentils, a glass of orange juice with breakfast, strawberries alongside fortified cereal. Vitamin C can increase non-haem iron absorption by up to 300%, according to research from the National Institutes of Health Office of Dietary Supplements.

To avoid blocking absorption: Calcium, tannins (in tea and coffee), polyphenols, and phytates (in raw bran and unsoaked legumes) all compete with or bind to iron and reduce absorption. This doesn't mean avoiding these foods — just try not to have your main iron-rich meal alongside a cup of tea, for instance. Leaving a gap of an hour or two makes a meaningful difference.

When Supplementation Makes Sense

If your ferritin is low, dietary changes alone may not be enough to catch up — especially if you're losing iron every month. Supplementation can be warranted, but it's worth knowing that not all iron supplements are created equal.

Ferrous sulphate is the most commonly prescribed form, but it's also the most likely to cause side effects (constipation, nausea, stomach cramping). Ferrous bisglycinate (also called iron glycinate or gentle iron) is a chelated form that is generally better tolerated and well absorbed — it's a good option if you've struggled with standard iron supplements in the past.

A few things to keep in mind:

• Take iron supplements on an empty stomach if you can tolerate it, or with a small amount of vitamin C-rich food to maximise absorption.
• Don't take iron at the same time as calcium supplements, antacids, or thyroid medication.
• Alternate-day dosing (every other day rather than daily) has some research support for reducing side effects while maintaining efficacy.
• Always work with a healthcare provider to establish the appropriate dose and duration — iron overload is genuinely harmful.

Addressing the Root Cause

Supplementing iron is vital for feeling better in the short term, but it's a sticking plaster if the heavy bleeding continues unchecked. There are several well-evidenced options for managing heavy periods worth discussing with your doctor:

• Hormonal IUS (Mirena): Highly effective at reducing menstrual blood loss — by up to 90% in some studies.
• Tranexamic acid: A non-hormonal medication taken during your period that reduces blood loss significantly.
• NSAIDs (e.g., ibuprofen): Reduce prostaglandins and can decrease bleeding by 25–30% when taken from the start of your period.
• Combined oral contraceptive pill: Regulates cycles and typically reduces flow.
• Treatment of underlying conditions: Addressing fibroids, polyps, or thyroid dysfunction if identified.

Supporting Your Body Through Your Cycle

Even without heavy periods, the week of menstruation is a time of increased nutritional demand. Being intentional about iron-rich eating in the days before and during your period — and pairing those foods with vitamin C — is a simple, powerful habit that supports your energy and recovery throughout each cycle.

Listening to your body isn't just self-indulgence. It's data. If you're consistently floored in the days after your period, if your "tired" feels different and deeper than ordinary fatigue, it's worth investigating. You deserve to function well for all 28 (or so) days of your cycle — not just the ones when you're not bleeding.