There are no official guidelines to assist in answering this question. I will search for relevant research papers instead.
From the Research
Normal Serum Lactate Dehydrogenase (LDH) Levels
- The normal rate of serum lactate dehydrogenase (LDH) levels is between 313-618 UI/L, as measured by spectrophotometry 1.
- Another study mentions that normal-range LDH levels are between 105-333 IU/L 2.
- A different study uses a stratification of >253 and ≤253 IU/l for serum LDH levels, according to the standard values used at their institution 3.
Factors Affecting LDH Levels
- Physical activity can transiently induce a greater total LDH level, still within its normal range 4.
- Strenuous and enduring physical activity can increase LDH levels, but these levels remain within the normal range 4.
- High serum LDH levels are significantly associated with the presence of metastasis and histological grade in soft tissue sarcoma patients 3.
Prognostic Value of LDH Levels
- LDH elevations superior to 10-fold the normal rate are a pejorative predictive criteria, with a mortality rate of over 50% 1.
- High serum LDH levels predict a terminal stage in metastatic cancer patients, with a median overall survival of 1.7 months 5.
- In patients with high-grade soft tissue sarcoma, high serum LDH levels are associated with worse disease-specific survival 3.