If you have been in practice for a few years, at some point a patient will have come in and complained about the horrendous abdominal pain, nausea, bloating and constipation they have from the iron prescribed by the NHS.
Remember the form is iron sulphate or iron fumerate, in a very high dose
They use a very high dose of 66mg (200 mg total), and they have to do that as it is very hard to get it to absorb from the gut into the blood.
The iron is in the ferrous state of iron with Fe 2+
In order to release iron from the sulphate/fumerate, you need stomach acid, HCL.
If you do not release the iron, the unit carries on down the gut without being absorbed, and then it creates havoc in the lower small intestines and colon.
Unabsorbed Fe²⁺ reacts with:
Mucosal cells → irritation and inflammation 
Gut bacteria → shifts microbiota, producing gas, bloating 
Hydrogen peroxide (H₂O₂) → catalyzes harmful free radicals via the Fenton reaction, damaging intestinal cells
Fenton Reaction:
Fe²⁺ + H₂O₂ → Fe³⁺ + OH• (hydroxyl radical, highly reactive)
All the inflammation makes for one angry intestinal tract, and the compliance is gone, and they stay low in iron.
Bear in mind many of the people low in iron, are low due to low HCL in the stomach, from acid inhibitors like PPI’s (Proton pump inhibitors) or just low output from old age. Thus the cannot tolerate the supplement they need due to the original cause of the deficiency.
Now if ferrous Fe 2+ does make it to the small intestines unbound via HCL, then the DMT1 will absorb it.
But, before that can happen, the alkaline environment in the small intestines, converts ferrous Fe 2+ to FERRIC 3+, and that does not go into the blood via DMT1.
The only way to convert it back to ferrous Fe 2+ is to add an electron, to go from Fe 3+ to 2+.
Hence vitamin C helps, as it donates an electron.
So, to bypass all this nonsense we use iron bisglycinate, a ferrous iron bonded to x2 glycine amino acids.
The iron in this does not need to be dissolved away from the glycine via stomach acid/HCL, so there are no issues with those low levels of HCL, creating the issues of deficiency in the first place.
It carries on down and is absorbed via a DIFFERENT TRANSPORTER, that sucks di/tripeptides (PepT1) into the cells and then into the blood.
Thus, the iron-glycine unit stays intact until it is in the cells of the gut lining, the disassociates.
This also means the iron is not at the mercy of oxalates, phytates etc, which can bind to unbound iron in the gut from food (or NHS ferrous fumerate/sulphate), making them in-absorbable.
It is thus GENTLE on the stomach with a higher absorption rate, often 200 – 400% higher.
Let me show this in an RCT on pregnant women.
Note the iron bisglycinate is only 24 mg vs 66 mg fumerate, 64 % lower dose.
Baseline ferritin 23-25 ng/ml
(Remember FERRITIN is your IRON RESERVES), you do not want it lower than 50, in some symptomatic people, I would push it up to 100 ng/ml.
Remember most people with iron deficiency are NOT anaemic, they have “non-anaemia iron deficiency” – often with restless legs, depression/anxiety, fatigue and chronic pain.
Re-read about that here 👇️
After 3 months
Check those numbers carefully 👀.
Not only is it far more absorbable, it also comes with very low rates of side effects.
Note the constipation in fumerate group is 67%, nausea nearly 50%, compared to 7% in the bisglycinate group.
If the patient does not have any gut symptoms I like to start them on x1 capsule, three times daily for 30 days.
If they have any gut stuff, start x1 daily 4-5 days, then increase x1/twice daily, and then if OK, x1 three daily.
If you want to diagnose exactly how much iron/ferritin they have before hand, or to fine tune them after you have started, then you can now do that with us, via our new sister company, OPTIMAL TESTING.
We are direct to practitioners ONLY (we do not talk to patients), so you create an account, and then order for each patient from the test menu.
Test goes to patient, and then you get the results back and pass them on to the patient.
Finger prick and venous options plus a blood draw finder.
In this case ferritin is £39, but for only £11 more, you get a full iron panel, all from a finger prick.
Why “optimal” testing?
Optimal Ranges vs Standard NHS Ranges
At Optimal Testing, our focus is not simply the absence of disease. It is the pursuit of optimal health.
What are standard NHS reference ranges?
Standard laboratory ranges are usually created by:
- Testing a large group of people considered “healthy”
- Removing individuals with diagnosed disease
- Defining the central 95 percent of results as the reference interval
- Labelling the highest 2.5 percent and lowest 2.5 percent as outside range
This means that for many blood markers, “normal” simply reflects what is statistically common within that population.
It does not necessarily mean biologically ideal.
In addition:
- The population sampled may include people with early dysfunction
- Nutrient insufficiency can still sit within range
- Chronic low grade inflammation may be common in the sample
- Ranges are designed primarily to detect disease, not optimise physiology
Standard ranges are therefore useful for identifying pathology, but they are not designed to guide optimisation.
Optimal ranges aim to reflect values associated with:
- Reduced disease risk
- Better metabolic efficiency
- Improved hormonal and neurological function
- Reduced inflammation
- Better long term health outcomes
These ranges are often narrower and based on outcome data rather than simple population statistics.
Optimal ranges may vary depending on:
- Age
- Sex