If you’re considering having a testosterone test in the near future, a new study from Boston’s Massachusetts General Hospital suggests that holding off on sugary drinks and food may be a wise move. The researchers found that participants who drank a glucose solution had testosterone levels that were significantly depressed, compared to controls.

The study, which was presented at the annual meeting of The Endocrine Society in June, followed 74 men: 42 of the men were healthy, 23 were considered “pre-diabetic” based on their blood sugar readings, and nine suffered from full-blown diabetes. The participants all drank a solution containing 75 grams of glucose, and then had their testosterone levels measured. Drinking a concentrated glucose solution causes blood sugar to rise considerably.

The researchers found that for up to two hours after consuming the glucose drinks, the men’s testosterone levels were depressed by about 25% compared to where they started. In fact, in 73 of the 74 men, the difference before and after testing was statistically significant. This trend was present whether the men were healthy, diabetic, or pre-diabetic. Fluctuations in other hormones or in insulin level did not seem to affect the changes in testosterone.

What’s more, of the 66 men with normal testosterone levels at the beginning of the study, 15 showed levels so low after consuming the glucose drink that they fell into the category of “hypogonadism” – or officially low testosterone.

Says researcher Frances Hayes, "[t]he decision to prescribe testosterone therapy is based on the result of a blood sample, so obtaining an accurate measurement of testosterone is key to making a correct diagnosis of hypogonadism.” He adds that "this research supports the notion that men found to have low testosterone levels should be reevaluated in the fasting state."

Hays also points out that the number of men diagnosed with low testosterone is increasing from year to year in this country – says Hays, “likely as a result of the obesity epidemic and our aging population.”