Taking coffee into the fasting window
The most common fasting error in the UAE is the 6am black coffee before a 7am lipid draw. Caffeine shifts glucose and fat metabolism enough to matter, and 'but it has no calories' does not rescue the sample. Water only, then coffee the second the plaster is on.
Testing the day after leg day
Hard training before a draw inflates creatine kinase, can bump ALT, AST and creatinine, and produces a panel that looks like organ trouble instead of a workout. Take one or two rest days before any panel that includes liver, kidney or muscle markers, and note recent training on the booking.
Hopping between labs and comparing the numbers
Different laboratories use different assay methods and reference ranges, so a small shift between two labs may be methodology, not biology. For anything you track over time — HbA1c, lipids, thyroid, ferritin — keep the same vendor and lab, and let the trend do the talking.