Name: Solgar Gentle Iron 20mg
Brand: Solgar
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By OffShift · 8 min read Last Updated: April 2026

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Quick Summary

Ferritin stores iron in your body — it's not the same as iron itself

Low ferritin causes fatigue long before you're technically anaemic

UK normal range is 15–300 µg/L, but "normal" and "optimal" are different

Under 30 µg/L often causes symptoms even if your GP says you're "fine"

Ferritin costs £15–£25 on a private blood test — cheapest of the energy tests

You've been tired for months. Your GP runs a full blood count, says you're "fine," and sends you home. If you've been through this and you still feel wrecked, the problem might be ferritin — the iron storage measure that gets left out of basic tests and often tells a different story.

Short Answer: Ferritin measures your body's iron stores. Low ferritin — even without technical anaemia — causes fatigue, brain fog, hair loss, and exercise intolerance. UK labs define normal as 15–300 µg/L, but most research suggests symptoms often start below 30–50 µg/L. If you're tired, female, or a regular blood donor, get ferritin checked. It's a cheap, high-value test.

Ferritin vs Iron: What's the Difference?

Iron and ferritin are related but different measurements.

Iron is the metal circulating in your blood right now, most of it bound to haemoglobin in red blood cells
Ferritin is the protein that stores iron in your liver, spleen, and bone marrow

Think of iron as the money in your wallet and ferritin as the money in your savings account. You can have enough in your wallet (normal iron) while your savings are empty (low ferritin). By the time both are low, you're anaemic — but symptoms usually start well before that.

Most GPs test "iron" via haemoglobin and red blood cell counts. That catches full-blown anaemia but misses the low-ferritin-with-normal-haemoglobin state that makes millions of UK adults feel tired without knowing why.

Why Ferritin Matters for Energy

Ferritin-bound iron is needed for:

Oxygen transport — iron in haemoglobin carries oxygen to muscles and brain
Mitochondrial function — your cells' energy factories depend on iron
Thyroid hormone conversion — iron is needed to convert T4 to active T3
Dopamine production — iron is a cofactor for mood-regulating neurotransmitters
Muscle function — myoglobin (muscle version of haemoglobin) needs iron

When ferritin is low, your body can often keep haemoglobin normal for months by stripping iron out of storage. But the other iron-dependent processes start to suffer — which is why low ferritin causes symptoms before anaemia shows up on a blood test.

Common Symptoms of Low Ferritin

Persistent fatigue that doesn't improve with sleep
Shortness of breath going up stairs
Hair thinning or shedding
Brittle nails with vertical ridges
Restless legs, especially at night
Cold hands and feet
Headaches
Difficulty concentrating ("brain fog")
Exercise intolerance (feeling worse after workouts)
Low mood or irritability
Craving ice, dirt, or starch (pica)

Any of these for more than a month is worth testing ferritin. The symptoms are non-specific — they overlap with thyroid problems, vitamin D deficiency, shift work fatigue, and a dozen other conditions — but ferritin is cheap to rule out.

UK Lab Reference Ranges

Range	Interpretation	NHS Action
Under 15 µg/L	Deficient	Treat with iron supplements
15–30 µg/L	Low	Often asymptomatic but may cause symptoms
30–50 µg/L	Low-normal	"Normal" on NHS — may still cause symptoms
50–100 µg/L	Normal	No action
100–300 µg/L	Normal-high	Usually fine but monitor
Over 300 µg/L	High	Investigate — could be infection, inflammation, or iron overload

The NHS considers anything above 15 µg/L as "not deficient." But a 2018 review in Blood found that many patients have persistent symptoms in the 15–50 µg/L range, and symptoms usually resolve when ferritin is brought above 50 µg/L.

Practical rule: if your ferritin is under 30 µg/L and you're tired, treat it regardless of what your GP says about "normal."

Who Is at Risk?

Ferritin tends to be low in:

Women of reproductive age — menstrual blood loss is the main cause
Pregnant women — iron demand doubles
Regular blood donors — each donation removes around 200–250mg of iron
Vegans and vegetarians — plant iron is less bioavailable
Athletes — especially endurance runners (foot strike haemolysis)
People with coeliac disease or IBD — poor absorption
Older adults — often due to unnoticed GI bleeding
People on long-term aspirin or NSAIDs — slow GI blood loss

If you fit two or more of these, get tested even if you feel fine. Low ferritin is easier to fix early than after years of depletion.

Reality Check: Why GPs Miss This

If you've been tired for months and your GP ran a full blood count that came back "normal," you haven't been ignored — you've been tested for the wrong thing. A full blood count (FBC) looks at red blood cell numbers, haemoglobin, and cell size. It catches anaemia, which only happens once ferritin has been depleted and haemoglobin has started to fall.

The pattern in patient forums and clinical audit data is consistent: people present with fatigue, hair loss, or brain fog, get told their haemoglobin is fine, and leave. Six months later they pay for a private ferritin test, discover it's 12 µg/L, start iron supplementation, and feel dramatically better within 6–12 weeks. You shouldn't have to go private for this, but for now it's often the fastest route to an answer.

How to Get Ferritin Tested

Options:

Ask your GP — NHS ferritin tests are available but often require you to advocate for them. Mention specific symptoms (fatigue, hair loss, brain fog, shortness of breath) rather than general tiredness.
Private finger-prick tests — Medichecks, Thriva, Forth include ferritin in most panels for £29–£79
Pharmacy tests — some Boots branches offer private blood tests including ferritin

The GP test is free but may be refused. Private tests are £15–£40 if you only want ferritin, or part of a wider panel for £50–£80.

Fixing Low Ferritin

If your ferritin is under 30 µg/L, you probably need more iron than diet alone will provide.

Dietary Iron (Slow but Steady)

Red meat — beef, lamb (haem iron, best absorbed)
Chicken and fish — smaller amounts of haem iron
Dark leafy greens — spinach, kale (non-haem, less bioavailable)
Lentils, chickpeas, beans — good plant source
Fortified cereals — check labels
Dried apricots and other dried fruit
Dark chocolate (70%+ cocoa)

Pair plant iron sources with vitamin C (peppers, citrus, tomatoes) to boost absorption. Avoid tea and coffee within an hour of iron-rich meals — tannins block absorption.

Iron Supplements

If you're deficient or symptomatic, diet alone often isn't enough. Options:

Supplement	Iron Dose	Notes
Ferrous sulphate 200mg	65mg elemental	NHS standard, cheap, commonly causes constipation
Ferrous fumarate 210mg	70mg elemental	NHS standard, similar side effects
Spatone water	5mg elemental	Very gentle, good absorption, slower
Solgar Gentle Iron 20mg	20mg elemental	Well-tolerated, better absorbed than sulphate
Floradix	10mg elemental	Liquid, well-tolerated, slower to raise levels

For most people who can't tolerate NHS-issued ferrous sulphate, Solgar Gentle Iron (buy on Amazon) is the sensible upgrade — bisglycinate form means dramatically fewer stomach side effects and better absorption. Around £10–£15 for 90 capsules (3 months at one per day).

Recent research suggests taking iron every other day results in similar or better absorption than daily dosing, with fewer side effects. Discuss with a pharmacist or GP before starting.

Iron supplements should be taken on an empty stomach if you can tolerate it, with orange juice or a vitamin C source. If that causes nausea, take with a small meal. Avoid taking with calcium, dairy, tea, or coffee.

Retest After 3 Months

Retest your ferritin 8–12 weeks after starting supplementation. If it hasn't moved or has dropped, there's likely an absorption problem or ongoing blood loss — see your GP.

When to Worry About High Ferritin

Ferritin above 300 µg/L (men) or 200 µg/L (women) deserves investigation:

Often raised during infection or inflammation (it's an acute phase protein)
Can indicate liver disease, heavy alcohol use, or metabolic syndrome
May indicate haemochromatosis (genetic iron overload) — affects 1 in 150 UK adults
Some cancers and autoimmune conditions raise ferritin

If your ferritin is high, your GP should investigate — don't ignore it just because "more is better than less."

Sources & Further Reading

Frequently Asked Questions

Is ferritin the same as iron?

No. Iron is the metal circulating in your blood, mostly bound to haemoglobin. Ferritin is the protein that stores iron for later use. You can have normal iron levels but low ferritin — meaning your reserves are running out even though the "current balance" looks fine.

What does low ferritin feel like?

Persistent fatigue that sleep doesn't fix, shortness of breath on stairs, hair thinning, cold hands and feet, brain fog, and sometimes restless legs at night. Symptoms usually start when ferritin drops below 30–50 µg/L, often before haemoglobin falls and anaemia shows up.

Can you have low ferritin but normal haemoglobin?

Yes — this is called iron deficiency without anaemia, and it's very common. Your body prioritises haemoglobin, so it can keep red blood cells normal by draining your ferritin stores for months. A full blood count will miss this; you need a specific ferritin test.

How long does it take to raise ferritin?

With oral iron supplementation, ferritin usually rises 10–30 µg/L per month. Going from 15 µg/L to 50 µg/L often takes 2–4 months. Symptoms improve faster than the numbers — most people feel better within 6–8 weeks even if ferritin is still climbing.

Should I take iron every day or every other day?

Recent research suggests alternate-day iron dosing results in similar or better absorption than daily dosing, with fewer side effects. Your body downregulates absorption after a large iron dose, so taking it daily can actually reduce total absorption. Discuss with a pharmacist before changing.

Can men have low ferritin?

Yes, though it's less common. Men with low ferritin usually have an underlying cause — GI bleeding, coeliac disease, long-term aspirin use, or heavy endurance training. If a man has low ferritin, it's worth investigating the cause rather than just supplementing.

This article is for informational purposes only and is not a substitute for professional medical advice. Always consult your GP before making changes to your diet, exercise routine, or health management.

What Is Ferritin and Why Does It Matter for Energy?