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Most Mistakes Happen Before the Lab Ever Sees Your Sample
A lot of DNA testing frustration doesn’t come from bad luck or a flawed company — it comes from a handful of avoidable missteps that happen well before results ever show up. Some cost you weeks of extra waiting. Others just lead to disappointment based on expectations the test was never going to meet in the first place.
Here’s what actually trips people up, based on the patterns that show up again and again.
1. Not Registering the Kit Before Collecting Your Sample
This is the single most common delay, and it’s entirely avoidable. Almost every company requires you to create an account and activate your kit’s unique barcode online before you collect your sample. Skip this step, and the lab has no way to match your sample to your account once it arrives — leading to processing delays or, in some cases, a request to send a new sample entirely.
The fix: Register online the moment the kit arrives, before you even open the collection tube.
2. Eating, Drinking, or Smoking Too Close to Collection
For saliva-based kits especially, food particles and other contaminants can interfere with sample quality, sometimes leading to a rejected sample and a replacement kit — adding weeks to your timeline.
The fix: Most companies recommend avoiding food, drink (other than water), gum, and smoking for at least 30 minutes before collection. Check your specific kit’s instructions, since exact timing varies.
3. Choosing a Kit Based on Price Alone, Without Checking Database Strength
The cheapest kit isn’t always the best value if your ancestry falls outside that company’s strongest reference regions. A budget-friendly test with a database that barely covers your background will leave you with a vague, unsatisfying ethnicity estimate regardless of price.
The fix: Match the kit to your known or suspected ancestry before comparing prices — our comparison of the major DNA testing kits breaks down which companies are strongest for which regions.
4. Expecting Ancestry Percentages to Be Fixed, Permanent Facts
A lot of first-time confusion (and occasional frustration) comes from ethnicity percentages shifting after a company updates its reference database. This is normal and doesn’t mean the original test was wrong — but it catches people off guard if they weren’t expecting it.
The fix: Go in understanding that ethnicity estimates are best-guess calculations based on current reference data, not permanent, unchangeable facts.
5. Not Thinking Through Unexpected Results Beforehand
This is less a technical mistake and more an emotional preparation gap. DNA testing can occasionally surface unexpected information — an unknown biological relative, a surprising gap in a family story, or an ethnicity result that doesn’t match family lore. People who haven’t considered this possibility beforehand are sometimes caught off guard in a way that’s harder to process than it needs to be.
The fix: Before testing, spend a few minutes genuinely considering how you’d want to handle an unexpected result, rather than assuming everything will simply confirm what you already know.
6. Ignoring the Privacy Policy Until After Testing
Consent settings around data sharing, relative matching visibility, and law enforcement access vary meaningfully between companies. Some people only look into these details after testing, when it’s harder to make an informed choice about settings they’ve already agreed to by default.
The fix: Read the consent options during sign-up, not after. Most companies let you adjust settings like relative-matching visibility, and it’s easier to set these up correctly from the start.
7. Buying a Combo Kit Without Actually Wanting Both Features
Combo kits like 23andMe bundle ancestry and health features together, but the price reflects that bundling. If you only care about one side of that equation, you may be paying for depth you’ll never use, when a specialized kit in just the category you want would have served you better and often cost less.
The fix: Get clear on whether you actually want ancestry, health insights, or genuinely both before choosing between a specialized kit and a combo option.
8. Assuming a Low Centimorgan Match Is a Confirmed Relative
Distant matches (particularly under 20 centimorgans) sit in a genuinely uncertain zone. Treating every match on your list as a confirmed relative, rather than a hypothesis worth investigating further, can lead to confusion or incorrect assumptions about your family tree.
The fix: Understand what your match numbers actually indicate — our guide on what a centimorgan actually measures breaks down how to interpret match strength more accurately.
A Quick Pre-Testing Checklist
Before you mail your sample back, it’s worth confirming: your kit is registered and activated, you’ve followed the pre-collection instructions (no food, drink, or smoking beforehand for saliva kits), you understand roughly what timeline to expect, and you’ve thought at least briefly about how you’d handle an unexpected result if one comes up.
Frequently Asked Questions
What’s the most common reason DNA test results get delayed? Failing to register the kit before mailing back the sample is the most frequent avoidable delay, since the lab can’t process an unregistered sample.
Can I fix a rejected sample without buying a whole new kit? Usually, yes — most companies send a replacement collection tube at no extra cost if your first sample was rejected due to insufficient quantity or contamination, though this does add time to your overall wait.
Is it normal for ethnicity results to change after testing? Yes, this is expected as companies update and refine their reference databases over time, and it doesn’t indicate an error in your original test.
The Bottom Line
Most DNA testing disappointment traces back to one of these avoidable missteps rather than the test itself being flawed. Register your kit properly, choose based on your actual ancestry and goals rather than price alone, and go in with realistic expectations about what the results will and won’t tell you — and the whole experience becomes considerably smoother.