A blood test is only as good as the preparation that goes into it. You can order the most comprehensive panel in the world, but if you train the day before, eat breakfast, or show up dehydrated, the results will be misleading.
Think of it this way: you would not weigh yourself after a heavy meal and call it your true body weight. The same principle applies to every marker in your blood. Preparation is not optional — it is the difference between data you can act on and data that sends you on a wild goose chase.
This cheat sheet covers everything you need to do — and not do — in the 72 hours leading up to your blood draw, with specific protocols for AAS users.
Three Days Out (D-3): Stop Training
This is the single most important preparation step, and the one most people skip. No resistance training, no high-intensity cardio, no intense physical activity for the full 72 hours. Light walking is fine.
Training causes measurable changes in your blood that persist for 48-72 hours in strength athletes:
- Creatinine elevation — makes your kidneys look stressed when they are not
- AST and ALT elevation — makes your liver look damaged when it is not
- CK elevation — can exceed 1000 U/L after heavy training
- Temporary shifts in electrolytes, cortisol, and inflammatory markers
If your AST/ALT come back elevated and you trained within 72 hours, you have no way to know whether it is muscle or liver. You will have wasted your test.
Two Days Out (D-2): Clean Up Your Diet
You do not need to eat like a monk, but avoid anything that could skew your results. This means no alcohol (it elevates GGT and triglycerides for days), no fatty meals (they affect lipoproteins), and no extreme changes in carbohydrate intake.
Stick to your normal maintenance diet. This is not the time for a cheat meal, a carb-loading day, or a prolonged fast. You want to measure your typical metabolic state, not an extreme one.
One Day Out (D-1): Stop Supplements
Many supplements directly affect blood markers. Stop all oral supplements 24 hours before your draw:
- Fish oil — lowers triglycerides (makes them look better than they are)
- Creatine monohydrate — elevates creatinine (falsely suggests kidney stress)
- Niacin — can skew lipid values and cause transient enzyme elevation
- Vitamin C in high doses — can interfere with glucose measurements
- Pre-workout stimulants — affect heart rate, BP, and stress markers
Injectable supplements (B12, AAS) should continue as normal — you are testing under your normal physiological conditions. Just stop the oral stuff.
12 Hours Out (D-1 Evening): Begin Fasting
Start your fast 10-12 hours before the draw. Water is allowed and encouraged. No coffee, no tea, no juice, no gum, no supplements — nothing but water.
Why fasting matters:
- Lipids: Non-fasted triglycerides are completely unreliable. LDL calculated from non-fasted values is also inaccurate.
- Glucose: Fasting glucose tells you about your metabolic health. Post-meal glucose tells you what you ate.
- Iron: Iron absorption from food can transiently elevate serum iron levels.
Set a timer on your phone: last bite of food at 8 PM, draw at 7 AM. Simple.
Morning of Draw (D-Day): Hydrate + Go Early
Dehydration concentrates your blood and elevates hematocrit, hemoglobin, and all protein-bound markers. For AAS users who already run elevated hematocrit, dehydration can push you from amber into red territory on paper — even if your actual value would be fine when hydrated.
Schedule your draw between 7:00 and 9:00 AM. Many markers follow circadian rhythms:
- Testosterone peaks in the early morning
- Cortisol follows a diurnal rhythm
- TSH varies significantly throughout the day
If you do multiple draws over time, keep the time consistent. A 3 PM testosterone reading cannot be compared to an 8 AM one.
The 500/500 Hydration Rule
Drink 500 mL of water before bed the night before your draw. Drink another 500 mL upon waking. This ensures you are well-hydrated without needing a bathroom break during the draw.
Proper hydration can drop hematocrit by 1-2 percentage points. For a competitive bodybuilder on a cycle at 52% Ht, that 1-2% can be the difference between a normal result and a flagged one. Do not give your doctor false data because you were thirsty.
- Take 72 hours off training before the draw
- Fast for 10-12 hours (water only)
- Hydrate: 500 mL before bed, 500 mL upon waking
- Draw between 7:00-9:00 AM
- Keep the same time for every draw
- Bring ID, lab form, and insurance card
- Stop oral supplements 24 hours before
- Eat a normal diet the day before (no extremes)
- Train within 72 hours — even light training skews results
- Drink coffee, tea, or juice before the draw
- Take oral supplements on the day of the draw
- Drink alcohol for 72 hours before the draw
- Eat a heavy or fatty meal the night before
- Schedule draws at different times across visits
- Remove the pressure bandage early
- Panic about a single out-of-range value
Required for lab identification. Driver's license or passport works.
Signed by your provider. Some labs accept electronic copies; others need a printed original. Check ahead of time.
Not always required, but useful if the phlebotomist has questions. Keep it simple: compound names, dosages, duration.
Something to eat immediately after the draw, especially if you are prone to lightheadedness. Protein bar or sandwich works.
Quick Prep Checklist — Download or Screenshot
72 hours before:
- Last training session done
- No alcohol
24 hours before:
- Stop all oral supplements
- Normal diet (no extremes)
12 hours before (evening):
- Start fasting (water only)
- Drink 500 mL water before bed
Morning of:
- Drink 500 mL water upon waking
- No coffee, tea, or food
- Draw at 7:00-9:00 AM
- Bring ID, form, snack
- Keep bandage on for 30-60 min
Common Trap: The Light Pump
After the Draw: What Comes Next
Labs typically return results within 24-72 hours. When your PDF arrives, upload it to GearCheck as soon as possible. Do not be alarmed if a single value comes back outside your usual range. Lab error happens in roughly 1-2% of tests.
If a result looks implausible — a hemoglobin of 20 g/dL when you usually run 16, or a creatinine of 2.0 when you are well-hydrated and rested — request a repeat test before making any decisions. One bad data point does not justify changing your protocol.