Should You Test Your Iron Before Taking an Iron Supplement?

What is ferritin?

Ferritin is the protein that stores iron in your body. A ferritin blood test doesn't measure the iron circulating in your blood directly — it measures your iron reserves, which is why doctors use it as the standard way to check whether you're actually low in iron, rather than guessing from symptoms.

Because ferritin reflects stored iron, it can pick up a shortfall before you become anaemic. A low ferritin result with an otherwise normal full blood count is sometimes called iron deficiency without anaemia — the stores are running low, but haemoglobin hasn't dropped yet. This is exactly the stage where testing catches something that symptoms alone would miss.

Signs of low iron

Low iron often shows up gradually, which is part of why it's easy to miss or attribute to something else. Common signs include:

• Persistent tiredness that doesn't improve with rest
• Pale skin or pale inner eyelids
• Shortness of breath during normal activity, such as climbing stairs
• Brittle nails, hair thinning, or nails that curve inward (koilonychia)
• Restless legs, especially at night
• Difficulty concentrating or "brain fog"
• Unusual cravings for ice or non-food items (a less common but recognised sign)

These signs overlap with many other causes of tiredness, including low vitamin D, low magnesium, poor sleep and stress — which is exactly why testing matters more than symptom-matching. Two people can have identical symptoms and completely different ferritin results.

What causes low iron in the first place

Iron becomes depleted for a few common reasons: not enough dietary iron (particularly on a vegetarian or vegan diet, since plant-based iron is absorbed less efficiently than iron from meat), increased loss through menstruation, increased demand during pregnancy and growth, and reduced absorption from digestive conditions such as coeliac disease or after weight-loss surgery. Regular blood donation and endurance training can also draw down iron stores faster than diet replaces them.

Who should test first

Testing before supplementing matters most for:

• Menstruating women, who lose iron monthly and are the group most likely to be low
• Pregnant women, whose iron needs increase substantially in the second and third trimesters
• Vegetarians and vegans, since plant-based (non-haem) iron is less readily absorbed than iron from animal sources
• Endurance athletes and regular blood donors
• Anyone with a digestive condition that affects absorption
• Men and post-menopausal women, for whom unexplained low iron can sometimes point to blood loss elsewhere and should always be discussed with a doctor rather than self-treated

Iron is one of the few nutrients where more isn't better. The body has no efficient way to get rid of excess iron once it's absorbed, so taking it without a confirmed reason can let levels build up over months and years, particularly in men, who don't have a monthly mechanism for iron loss.

How to get tested in South Africa

A ferritin test is a standard blood test available through your GP, a pathology lab such as Lancet, Ampath or PathCare, or some pharmacy health clinics. Most doctors will request it alongside a full blood count and, if needed, additional markers such as transferrin saturation or C-reactive protein, since inflammation can temporarily raise ferritin and mask a true deficiency. No special preparation is usually required, though your doctor may ask you to fast beforehand depending on what else is being tested at the same time.

What your results mean

Reference ranges vary slightly between labs, but low ferritin generally means your iron stores are depleted, even if your haemoglobin is still in the normal range. Very high ferritin can also be a sign of inflammation, liver strain, or — less commonly — iron overload conditions such as haemochromatosis. Because ferritin can be affected by factors other than iron status alone, results should always be interpreted by your doctor alongside your symptoms and other blood markers, not read in isolation or compared to a number you found online.

Choosing an iron supplement

If your doctor confirms low iron, the form matters. NutriZen Iron+ uses iron bisglycinate, a chelated form that's generally gentler on the stomach than standard ferrous sulphate, paired with buffered vitamin C and spirulina to support absorption and red blood cell formation. Take iron away from coffee, tea, dairy and calcium supplements, which all reduce how much you absorb — see our guide on what not to take with iron supplements for the full list.

Retest after two to three months of supplementing to confirm your levels have moved in the right direction, and stop supplementing once your doctor confirms your stores are back in range rather than continuing indefinitely.