Research shows that laypeople rely more on their capabilities to make decisions about science‐based knowledge claims after reading comprehensible compared with less comprehensible topic information. This can be problematic, because complex science‐based issues usually cannot be understood fully without experts' further advice. The present study investigated whether making readers aware of the ‘epistemic topic complexity’ of an issue (i.e., the extent of existing topic knowledge, the complexity of relationships between concepts, and the existence of multiple expert perspectives) can mitigate this influence of comprehensibility. Undergraduate students read comprehensible or less comprehensible health texts with topic knowledge being described as complex, uncomplex, or not described at all. They reported whether they agreed with the claim and would rely on their decision. Results showed that after reading comprehensible information, participants' reliance on their decision increased less when they considered topic knowledge to be complex. Practical implications of the findings are discussed. Copyright © 2014 John Wiley & Sons, Ltd.