Glutamate Dehydrogenase (GLDH) Unit Converter
Glutamate Dehydrogenase (GLDH) Unit Converter
Convert glutamate dehydrogenase between U/L, IU/L, µkat/L and nkat/L, with the sex-specific reference limits German laboratories publish. GLDH is a mitochondrial hepatocyte enzyme, and its interest is that it stays put when ALT rises from muscle.
Glutamate dehydrogenase converter
Activity unitsGLDH 3.5 U/L in a woman
Formula and conversion factor
U/L = µkat/L × 60
nkat/L = U/L × 16.667
- U
- 1 unit = 1 µmol of substrate converted per minute under the assay’s own conditions
- kat
- 1 katal = 1 mol of substrate converted per second — the SI unit of catalytic activity
- ÷ 60
- the whole of the conversion. Per-minute against per-second, nothing else; no molecular weight is involved because activity is not a mass
- IU/L
- numerically identical to U/L. The I adds nothing here
- what does not convert
- a result reported in ng/mL or µg/L is a mass concentration measured by immunoassay, and there is no factor between it and U/L. The two tests count different things
Worked example
GLDH 3.5 U/L in a woman
3.5 ÷ 60 = 0.058 µkat/L
= 58 nkat/L = 3.5 IU/L
Below the female limit of 5.0 U/L (0.083 µkat/L)
The same 3.5 U/L in a man sits well below his 7.0 U/L limit — the sex difference is about 40%, which is larger than the analytical imprecision of the assay
Reference limits and where they come from
| Source | Limit | Method |
|---|---|---|
| University Hospital Cologne, heparin plasma | Women < 5.0 U/L, men < 7.0 U/L | Roche cobas c702, UV kinetic at 340 nm, 37 °C |
| DiaSys, quoting DGKC | Women ≤ 5.0 U/L, men ≤ 7.0 U/L | DGKC method |
| Aubrecht et al. 2025, research cohorts | 10 U/L, not sex-specific | Clinical chemistry analyser, both sexes pooled |
GLDH against ALT
| GLDH | ALT | |
|---|---|---|
| Where in the cell | Mitochondrial matrix | Cytosol |
| Where in the lobule | Concentrated centrilobularly | More evenly distributed, periportally weighted |
| Other tissues | Kidney, intestine, muscle and salivary gland contribute little to serum | Skeletal muscle contributes materially |
| In 128 subjects with muscle injury | Above the upper limit in 12 | Above the upper limit in 53 |
| Discrimination of hepatocellular injury | Area under the ROC curve 0.958 across the combined cohorts | The comparator, correlated at r = 0.89 |
Why a mitochondrial enzyme tells you something ALT does not
Glutamate dehydrogenase catalyses the reversible deamination of glutamate to 2-oxoglutarate, and in humans it lives in the mitochondrial matrix of hepatocytes, concentrated in the centrilobular zone. Two consequences follow, and they are the whole of its clinical interest. Because it is mitochondrial, serum GLDH rises only when injury is severe enough to breach the mitochondrial membrane, not merely the plasma membrane — a cytosolic enzyme like ALT leaks earlier and more readily. And because its extrahepatic contribution to serum is small, a raised GLDH points at liver in a way a raised ALT does not.
That second property is being taken seriously in drug-induced liver injury. ALT is the standard hepatocellular signal, but skeletal muscle contains ALT too, so a rise in a patient with myopathy, rhabdomyolysis, muscular dystrophy or simply heavy exercise raises a question the ALT cannot answer. In the largest recent evaluation, of 128 subjects with muscle injury 53 had an ALT above the upper limit of normal while only 12 had a raised GLDH; across the paper’s combined hepatic cohorts GLDH discriminated hepatocellular injury with an area under the ROC curve of 0.958. That is the specific use: not replacing ALT, but arbitrating when ALT is ambiguous.
Two cautions belong on the same page. The first is that the diagnostic thresholds quoted in that work — 25 U/L and 48 U/L — are regression equivalents of an ALT at three and five times its upper limit, derived so that a GLDH-based study could be designed in the language of existing ALT criteria. They are not thresholds any guideline has adopted, and Hy’s law is written in ALT and bilirubin, not GLDH. The second is the reference limit itself. German clinical laboratories publish sex-specific limits — under 5.0 U/L in women and under 7.0 U/L in men, a difference of about 40% — while the research work used a single pooled limit of 10 U/L. A value of 8 U/L is therefore abnormal by one standard and normal by another, and no honest page can collapse that.
GLDH is routine in continental Europe and rare in British and American laboratories, and it is a standard part of the liver panel in veterinary practice, where it is the hepatocellular marker of choice in horses, cattle and other large animals, and in birds, reptiles and amphibians, whose ALT is uninformative. Its centrilobular distribution also means it is relatively more raised than ALT after hypoxic or ischaemic injury, which is where the centrilobular zone suffers first.
An enzyme activity is defined by the assay that measured it — its substrate, its buffer, its temperature. A reference interval belongs to that method and does not travel to another one, which is why the interval on your own report is the one to read the result against.
Frequently asked questions
How do I convert GLDH from U/L to µkat/L?
Divide by 60. A GLDH of 3.5 U/L is 0.058 µkat/L, or 58 nkat/L. The factor is the katal definition and is the same for every enzyme activity.
What is a normal GLDH?
It is sex-specific. University Hospital Cologne publishes under 5.0 U/L for women and under 7.0 U/L for men on a Roche UV kinetic assay at 37 °C, and DiaSys quotes the same 5.0 and 7.0 figures from the DGKC. A recent research study used a single limit of 10 U/L for both sexes, so check which standard your report is using.
Why use GLDH instead of ALT?
Mainly when ALT might not be coming from the liver. Skeletal muscle contains ALT; GLDH is effectively liver-specific in serum. In one study of 128 people with muscle injury, 53 had a raised ALT and only 12 a raised GLDH. GLDH is also relatively more raised after centrilobular injury, because that is where the enzyme is concentrated.
Is there a GLDH threshold for drug-induced liver injury?
Not one that any guideline has adopted. The figures of 25 and 48 U/L that appear in the literature were derived by regression as the GLDH equivalents of an ALT at three and five times normal, so that studies could be specified in familiar terms. Hy’s law remains written in ALT and bilirubin.
Why is GLDH used in veterinary medicine?
Because ALT is not informative in large animals, birds, reptiles or amphibians, while GLDH is a reliable hepatocellular marker in all of them. It is a mitochondrial enzyme concentrated in the centrilobular hepatocytes, which also makes it sensitive to hypoxic liver injury.
Related calculators
References
- Aubrecht J, Schomaker S, Amacher DE, et al. Serum glutamate dehydrogenase activity enables sensitive and specific diagnosis of hepatocellular injury in humans. Toxicol Sci. 2025;203(2):171–180.
- Universitätsklinikum Köln, Institut für Klinische Chemie. Leistungsverzeichnis: GLDH — reference range women <5.0 U/L, men <7.0 U/L; UV kinetic assay at 37 °C.
- DiaSys Diagnostic Systems. Glutamate dehydrogenase (GLDH) reference ranges, quoting DGKC: women ≤5.0 U/L, men ≤7.0 U/L.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.