At Any Lab Test Now®, we make testing simple: most visits take about 15 minutes, doctor’s orders are provided, and results are typically available in 1–3 business days with transparent pricing.
Use these tips to avoid common pitfalls—then walk in or schedule online to Take Control Of Your Health!
1) Not Fasting Properly
- Why it matters: Food and drink (other than plain water) can raise glucose and insulin and transiently elevate triglycerides; even black coffee may affect glucose and catecholamines. Milk/cream, sugar-containing gum, alcohol, and caloric beverages can skew results.
- Typical fasting window: 8–12 hours for a lipid panel and fasting glucose; some labs specify 12 hours for triglycerides.
- Special notes: Plain water is encouraged to avoid hemoconcentration. For OGTT, follow prep precisely. Some tests (A1c, many hormones) don’t require fasting—confirm instructions.
2) Skipping Essential Medications
- Why it matters: Stopping chronic meds (e.g., levothyroxine, antihypertensives, antiepileptics) can acutely change lab values and misrepresent your baseline control.
- Take vs. hold: Generally, take routine morning medications with a small amount of water unless told otherwise.
- Exceptions: Some tests require holding meds (e.g., ACE inhibitors before aldosterone/renin ratio; biotin-containing supplements before certain immunoassays).
- Tip: If a drug level is being measured (e.g., valproate, digoxin), confirm timing (often a trough level—right before the next dose).
3) Getting Blood Work Done While Sick
- Why it matters: Acute illness can elevate CRP/ESR, WBC count, fibrinogen, and transiently alter liver enzymes, ferritin, thyroid function, and glucose.
- When to wait: For non-urgent monitoring (lipids, routine wellness labs), postpone 1–2 weeks after recovery.
- When not to wait: If the test evaluates the illness (e.g., CBC for infection, CRP for inflammation), proceed as instructed.
4) Taking Supplements (Especially Biotin)
- Why it matters: High-dose biotin (>5–10 mg/day) can interfere with biotin–streptavidin immunoassays, causing falsely high or low results (thyroid tests, troponin, sex hormones, cortisol, some vitamin assays).
- Hold times: Stop biotin 24–72 hours before testing; very high doses may require 3–7 days.
- Other interferers: Very high-dose vitamin C can affect some glucose meters and assays.
- Tip: Biotin is common in hair/skin/nail formulas—check labels and bring a photo/list of supplements.
5) Being Under-Hydrated
- Why it matters: Dehydration concentrates blood components (hemoconcentration), artificially raising hematocrit/hemoglobin, albumin, and some electrolytes—and it makes venipuncture harder.
- Practical target: Drink water as usual; a glass or two in the morning helps. Avoid excessive water-loading (risk of low sodium).
- Signs of under-hydration: Dark urine, dizziness, hard-to-find veins.
6) Not Telling Your Provider About Medications/Supplements
- Why it matters: Many agents alter labs:
- NSAIDs: can affect kidney function (creatinine, eGFR)
- PPIs: can alter magnesium and vitamin B12
- Steroids: raise glucose and WBCs; suppress CRP
- Oral contraceptives: change binding proteins (e.g., TBG), affecting total hormone levels
- Herbals: ashwagandha may affect thyroid labs; St. John’s wort alters drug metabolism
- Action: Provide dose, timing, and duration. Include OTCs and herbals.
7) Exercising Before Lab Work
- Why it matters: Strenuous exercise can raise CK/AST, lactate, and potassium; lower triglycerides temporarily; and acutely affect cortisol/testosterone.
- Guideline: Avoid vigorous exercise for 24 hours before baseline labs. Light activity is fine.
- Cardiac/muscle injury workups: Avoid exercise unless instructed.
8) Eating High-Fat Meals
- Why it matters: High-fat meals can cause postprandial lipemia (milky serum), raising triglycerides and affecting LDL calculation (Friedewald formula). Some inflammatory markers may also shift.
- Timing: Avoid fatty meals the evening before fasting lipid panels; adhere to the 8–12 hour fast.
- Note: Non-fasting lipid panels are sometimes acceptable, but triglycerides vary post-meal—confirm with your clinician.
9) Testing Too Soon After Starting a New Medication
- Why it matters: Many meds need time to reach steady state or exert effects:
- Statins: full lipid changes in ~4–12 weeks
- Levothyroxine: TSH equilibrates in ~6 weeks
- Iron therapy: ferritin/hemoglobin changes over weeks to months
- Tip: Ask for the recommended retest interval to avoid premature adjustments.
10) Waiting Until the Day Before Your Appointment
- Why it matters: Labs need processing time; late draws risk incomplete results and limited decision-making during your visit.
- Best practice: Get labs 3–7 days before the appointment (or per clinic guidance). For time-sensitive tests (e.g., trough levels), align timing precisely.
Additional Best Practices
- Timing matters
- Morning draws preferred for some hormones (cortisol, testosterone), iron studies, and fasting tests
- Circadian variation affects ACTH, cortisol, some cytokines
- Avoid alcohol and large caffeine intakes
- 24 hours prior for panels sensitive to glucose, triglycerides, liver enzymes, catecholamines
- Menstruation and recent bleeding
- Can affect iron studies and CBC—note timing on the requisition
- Tourniquet time and posture
- Prolonged tourniquet use and posture changes affect potassium, protein, calcium; minimize fist-clenching and stasis
- Specimen-specific prep
- Some tests (renin/aldosterone, catecholamines, 24-hour urine) have strict posture/diet/med restrictions—follow lab instructions closely
Quick Prep Checklist
- Fast 8–12 hours if instructed; water only
- Take routine prescription meds unless told to hold
- Skip biotin and non-essential supplements for 24–72 hours (or per instructions)
- Avoid strenuous exercise for 24 hours
- Hydrate with water; don’t overdo
- No alcohol the day before; limit caffeine the morning of
- Schedule labs 3–7 days before your appointment
- Bring a complete list of medications and supplements (with doses)
- Note any recent illness, menstruation, or major changes (diet, meds)
- Confirm any special timing requirements (morning draw, trough level)
Why Choose Any Lab Test Now®
- Convenient, fast visits: Most take ~15 minutes; walk-ins welcome.
- No doctor’s order needed: Direct-access to thousands of tests and panels.
- Transparent pricing and privacy: See costs before you come; results delivered electronically and kept confidential.
- Nationwide locations: Find the nearest testing center and plan on results in 1–3 business days.
Ready for accurate, stress-free blood work? Walk in or schedule online—Take Control Of Your Health!
