Let's start this post with a little anecdote... one of frustration. I had a patient with a history of low iron who was taking Feramax (a polysaccharide-ion complex form of iron) for several years as instructed by their medical doctor. On this patient's latest blood work it showed that their iron levels (as measured by "ferritin" storage) hadn't budged an inch.
Yes, it's frustrating when a medication or supplement isn't working, but what was more frustrating was that even after seeing these test results, the MD told the patient to keep taking the Feramax.
Now, I have nothing against Feramax, in fact, it can be a fantastic supplemental iron and has been known to be more gentle on the stomach than other forms like ferrous gluconate. I've prescribed it among other iron supplements in the past. But it obviously wasn't helping bring iron levels up in this patient. This often means that there is an issue with bioavailability and absorption.
When left in the hands of patients, it's easy to become confused with several types of iron supplements available. While I was a pharmacy assistant, customers would come in regularly looking for iron as directed by their doctor. Of course, without any actual prescription or direction, customers typically went for the cheapest one on the shelf. But quality matters here and no one was educating these customers (and at the time, legally I wasn't allowed to since I was still a student) on the differences between these supplements.
Some iron supplements like ferrous gluconate and ferrous fumarate can be harsher on the stomach; Some can cause nausea and constipation; Many of them interact with other minerals such as calcium, and not all of them have a stellar absorption rate. In fact, the absorption rate of most iron supplements is less than 5%.
It's also important to note the needs of each individual. For those who are vegan or vegetarian, they may wish to avoid heme iron supplements - heme iron being derived from animal hemoglobin (typically porcine). Heme iron has about 3x more bioavailability to non-heme or elemental iron, making it an excellent treatment for increasing iron levels in those who are anemic.
Another elemental form of iron is iron glycinate or iron bisglycinate chelate. This form of iron is protected by glycine molecules so that it doesn't interact with other minerals in the GI tract; As well, it has better bioavailability than ferrous gluconate. Because of how gentle it is (and cost effective!), this one tends to be a client favourite.
The take home message here is not to be discouraged when one type of supplement isn't working. Even with something like B12... if taking an oral supplement isn't working, there's a better chance at increasing B12 levels via injection as the injected B12 is delivered directly into the muscle and avoids the stomach and GI tract altogether.
The wonderful thing about naturopathic doctors is the abundance of nutrition training we have in comparison to medical doctors. Try not to be discouraged on your path to wellness, but know that there is usually an alternative if something isn't working for you.
ND's Notes: It is not advised to take an iron supplement without the supervision of an MD or ND via blood work. The toxicity associated with excess iron can be extremely dangerous.