Biohacker Bryan Johnson reveals autoimmune gastritis diagnosis: 'My stomach is eating itself'

Bryan Johnson, the technology entrepreneur and anti-ageing advocate known for spending millions of dollars annually on health optimisation and anti-ageing interventions, has revealed that he has been diagnosed with autoimmune gastritis (AIG), a chronic autoimmune disorder in which the body's immune system attacks the stomach lining.

Biohacker Bryan Johnson reveals autoimmune gastritis diagnosis in a lengthy post

In a lengthy post shared on X, Johnson described his diagnosis as both a personal and scientific challenge, saying he plans to publicly document his attempts to better understand and potentially treat the condition.

"Bad news #1: I have an autoimmune disease. My stomach is eating itself (sic)," Johnson wrote.

He added: "Bad news #2: 2–5% of people have this, too. Likely more, because it hides (sic)."

Johnson, 48, who has gained international attention through his longevity project Blueprint and his extensive experimentation with health monitoring and age-reversal therapies, said he was diagnosed with autoimmune gastritis in May after years of unexplained low iron stores and a history of autoimmune thyroid disease.

"Good news: I'm going to try and solve it. Will share all (sic)," he wrote.

According to Johnson, his medical history dates back to a diagnosis of hypothyroidism at the age of 21, for which he has long received hormone replacement therapy. However, he said that for more than a decade, doctors were unable to determine why he persistently suffered from low ferritin levels despite dietary interventions and supplementation.

"My hypothyroidism got diagnosed when I was 21 years old with a routine blood draw (sic)," Johnson wrote. "What I didn’t know was that something else was going on inside my body: my stomach had begun attacking itself (sic)."

Johnson said his medical team revisited years of clinical data after he overhauled his healthcare programme earlier this year as part of what he described as the groundwork for his "Immortals Care" protocol, which he said costs around $1 million annually.

The investigation involved a colonoscopy, upper endoscopy, blood biomarker analysis and multiple gastric biopsies. According to Johnson, tests revealed elevated anti-parietal cell antibodies, while biopsies confirmed early-stage autoimmune gastritis.

"We now had a formal diagnosis. I have autoimmune gastritis AIG. My stomach is eating itself (sic)," he wrote.

Autoimmune gastritis is a relatively uncommon but often underdiagnosed condition in which the immune system attacks cells in the stomach that produce acid and intrinsic factor, a protein necessary for vitamin B12 absorption. Medical experts say the disease can remain asymptomatic for years before causing iron deficiency, vitamin B12 deficiency, anaemia and, in some cases, an increased risk of gastric cancer and neuroendocrine tumours.

Johnson argued that the condition frequently goes undetected because standard medical assessments tend to focus on anaemia.

"And the earliest clue, low ferritin, is the one standard medicine waves through," he wrote. “Low iron stores get normalised and rarely investigated at all when anaemia hasn't shown up yet. That blind spot is what hid mine for a decade (sic).”

He said his iron deficiency has since been corrected through a 1,000 mg intravenous iron infusion and that he plans to pursue extensive monitoring and experimental research approaches to better understand the disease's underlying mechanisms.

Johnson outlined a multi-tiered strategy involving routine biomarker monitoring, repeat biopsies, immune profiling and exploratory therapeutic approaches, including interventions targeting immune pathways, regulatory T cells and, potentially, engineered cell therapies. He acknowledged, however, that many of the approaches remain experimental.

"To be clear: there's no approved cure for autoimmune gastritis today. Medicine treats it as something to manage, not solve (sic)," he wrote.

The entrepreneur also used his diagnosis to advocate for proactive health monitoring and preventative medicine, arguing that the absence of symptoms does not necessarily indicate good health.

"You too may have a lurking health issue that is undiagnosed and could increase in severity from unhealthy life choices, without your knowing (sic)," he wrote. "The absence of symptoms is not the presence of health (sic)."

Johnson concluded his post with a broader reflection on health, mortality and human priorities, urging people to prioritise their wellbeing.

"We fill our days mostly on things that are trivial next to what we ultimately care about," he wrote. "We know, deep down, however, that in the noise of it all, health is easily forgotten until it’s the only thing that matters (sic)."

Johnson said he intends to continue sharing updates on his condition and on any future research aimed at understanding or potentially treating autoimmune gastritis.