This drinking glass shows a three-month buildup of iron from the well water. CLR removes the iron, and the glass looks clear for a few days before the process starts over again.

This post was reviewed on Sept. 13, 2026.

I have two reasons to revisit the topic of iron and laminitis.

One is an email I received Nov. 26, 2012, from a woman whose 6-year-old mare has been suffering from laminitis since February 2011. The mare was on supplements for a long time, including expensive laminitis supplements, and she still was chronically lame. A month ago, the owner went against conventional wisdom and turned the mare out on a 100-acre pasture with a stream running through it. The horse is now sound and bucking and playing like a foal. Needless to say, the owner has been pleasantly surprised. She’s investigating if the culprit may have been her well water, since the mare is now drinking exclusively from the stream. The owner describes her well water as I would mine: It turns everything orange and tastes bad.

The owner asked me about testing her mare for iron overload.

I suggested she do what I failed to do: a serum ferritin test.

I had Robin Hood tested for iron overload on Oct. 12, 2012, but I believe I asked for the wrong test. I did a serum iron test, which tested the amount of iron currently in Robin’s blood. A local zoo did the test. Robin’s serum iron level is 2.9, with normal being up to 2.6 and the toxic level being 4.6. These numbers are specific to the zoo’s lab. I can’t compare these numbers to the results of other labs.

At any rate, it would be more productive to know the amount of iron stored in Robin’s organs, and this requires a serum ferritin test, which is on our to-do list.

According to veterinarian and author Eleanor Kellon, the higher the serum ferritin, the more iron is stored in the body tissues. Primary storage sites are the liver and the spleen. Kellon says some horses are so heavily loaded with iron that their livers are found to be black on postmortem examinations.

When I first brought up iron overload as a possible cause of my horses’ problems, one prominent laminitis researcher told me iron was studied as a possible cause of laminitis and failed to produce laminitis in study subjects.

However, the human world is completely on board with iron being linked to diabetes. I’ve been hearing this from journalism friends with good sources, but I’m also seeing it in clinical research, which leads me to the second reason I’m revisiting this topic. I just stumbled over a study published September 10, 2012, in the Journal of Clinical Investigation that leads off with the sentence: “Iron overload is associated with increased diabetes risk.”