N-Methylhistamine (urine)

N-methylhistamine is formed when the body breaks down histamine. It is measured in urine. Unlike histamine in stool, which comes mainly from the gut, it reflects histamine turnover in the whole body.

How histamine is broken down

Histamine is broken down in two ways: in the gut and outside the cells mainly by the enzyme DAO, inside the cells by histamine N-methyltransferase (HNMT). The second pathway produces N-methylhistamine, which is excreted by the kidneys. Most of the body's own histamine is stored in mast cells.

High methylhistamine – what happens in the body?

A raised value shows that more histamine is being released and broken down – for example with allergic reactions, increased activation of mast cells or shortly after very histamine-rich food. Histamine widens blood vessels (flushing, feeling of warmth, headache, drop in blood pressure), makes them leakier (swelling, hives), triggers itching, narrows the airways, stimulates stomach acid and speeds up gut movement.

Low methylhistamine – what does it mean?

A low value is unremarkable and indicates low histamine turnover. Together with DAO and histamine in stool, it helps to assess where histamine arises and how well it is broken down.

The interpretation is given in your report.