I finished my IB in Tokyo during the May 2023 session with a 45. Now I have offers from Cambridge HSPS, HKU, and HKUST. Selecting your HLs feels overwhelming when you want to keep every scientific door open. Most students struggle with whether to take Physics or Chemistry at Higher Level for general science paths.
Your subject choices dictate which universities actually consider your application. I spent months mapping out the overlap between different science degrees. This guide shows you exactly which combinations satisfy top-tier entry requirements. You will see why some HLs carry more weight than others in the eyes of admissions officers.
The Non-Negotiable HLs: Mathematics and Two Sciences
For any serious Natural Sciences application, particularly in the UK, your Higher Level (HL) choices are paramount. You absolutely must take HL Mathematics (Analysis and Approaches) and two HL sciences. This is the bedrock. Universities like Cambridge, Oxford, Imperial, and UCL explicitly state this requirement, often specifying Physics, Chemistry, or Biology. Without this combination, your application for Natural Sciences will likely be immediately disregarded, regardless of your predicted score.
Why two sciences? Natural Sciences degrees are designed to provide a broad scientific foundation before specialization. Demonstrating proficiency across multiple scientific disciplines at a high level is crucial. For example, a Cambridge Natural Sciences applicant might start with three sciences (e.g., Physics, Chemistry, Biology) in their first year, then specialize later. Your IB HLs need to reflect this capacity for breadth and depth. My peers applying for Natural Sciences almost universally followed this rule, opting for combinations like HL Math AA, HL Physics, HL Chemistry, or HL Math AA, HL Chemistry, HL Biology.
Mathematics AA HL: Essential for All Science Streams
Let's be unequivocally clear: if you are applying for Natural Sciences, you need Mathematics: Analysis and Approaches (AA) at Higher Level. Mathematics: Applications and Interpretation (AI) HL, while challenging in its own right, is generally not accepted for competitive science degrees, especially in the UK. Universities expect a strong theoretical grounding in calculus, algebra, and vectors that AA HL provides. This is fundamental for understanding physics, advanced chemistry, and quantitative biology.
Even if your primary interest leans towards biology, the quantitative demands of modern biological research (bioinformatics, computational biology, biophysics) make AA HL indispensable. My advice: if you're even considering Natural Sciences, commit to AA HL. It's tough, but it's a gatekeeper subject. If you find yourself struggling severely with AA HL, it might be an early indicator that a highly quantitative science degree isn't the best fit, or that you need to dedicate significant extra study time.
Physics and Chemistry: The Most Versatile Pair
If you're unsure which two sciences to pick, HL Physics and HL Chemistry form the most versatile combination for Natural Sciences. This pairing keeps almost all doors open, from physical sciences (e.g., Materials Science, Engineering, even some Computer Science programs) to chemical and biological sciences. Many Natural Sciences programs require or strongly prefer at least one of these two. For instance, if you want to specialize in Physics or Chemistry later, having them at HL is a prerequisite.
This combination also aligns well with university expectations for a rigorous scientific foundation. Physics teaches problem-solving and mathematical application to natural phenomena, while Chemistry provides the understanding of matter and its interactions. These two subjects often complement each other, with concepts from one discipline enhancing understanding in the other. It's a demanding combination, but it's the safest and most recommended route for broad Natural Sciences applications.
Biology HL: Strategic for Life Sciences Focus
If your passion lies firmly in the life sciences – perhaps you envision specializing in Biochemistry, Genetics, or Ecology – then HL Biology alongside HL Chemistry (and HL Math AA) is an excellent choice. This combination is highly regarded for biological-focused Natural Sciences tracks. However, be aware that dropping Physics HL might limit your options if you later discover a strong interest in more physically-oriented fields within Natural Sciences, such as Earth Sciences or Materials Science.
Universities in the US and Hong Kong might be slightly more flexible with HL combinations than the UK, but for top-tier programs, the 'Math AA + two sciences' rule still largely holds. When considering Biology HL, ensure you're genuinely passionate about it, as it's a content-heavy subject. The depth of understanding required for the IB exams (especially Paper 3) goes beyond memorization and demands critical analysis and experimental design knowledge.
The Role of Your Third HL: Breadth or Depth?
While the core is Math AA HL and two sciences, some students opt for a third HL (making it four HLs total). This is common in some international schools. If you do this, consider if it genuinely adds value. A fourth HL in a science or related subject (e.g., Computer Science HL if you're leaning towards computational aspects) can demonstrate exceptional academic ability and commitment. However, do not take a fourth HL if it compromises your predicted grades in your core three. A 45 with three strong HLs is always better than a 42 with four mediocre ones.
Alternatively, if your school permits, a humanities or arts HL can demonstrate intellectual breadth, which some US universities appreciate. However, for UK Natural Sciences, this is less critical than your core science HLs. My own experience with HSPS meant I had a humanities-heavy HL set, but for Natural Sciences, the focus is squarely on the quantitative and scientific rigor. Prioritize achieving top grades in your essential Math AA and two science HLs above all else.
Strategic SL Choices: Language and Humanities
Your Standard Level (SL) subjects, while less critical than HLs, still play a role. Most students will take Language A (their native language or strongest language) and Language B (a second language) at SL. This is standard and expected. For your third SL, if you're not doing a fourth HL, a humanities or arts subject can be a good choice to maintain intellectual balance and demonstrate a well-rounded profile, especially for US applications.
Consider subjects like History, Economics, or Psychology at SL. They can develop critical thinking and essay writing skills, which are transferable even to scientific communication. However, avoid taking a 'filler' SL that doesn't genuinely interest you or contribute to your skill set. The key is to ensure your SLs don't detract from your focus on achieving high grades in your demanding HL sciences and math.
Common Pitfalls to Avoid
One major pitfall is choosing Math AI HL instead of Math AA HL for Natural Sciences. This is a common mistake that can instantly disqualify you from many top programs. Another is taking only one science at HL. Again, this is a red flag for UK universities particularly. Always check the specific university and course requirements. Don't assume that 'any science' is sufficient; some programs will have specific preferences (e.g., 'Chemistry HL is essential').
Finally, don't overload yourself. While a 45 is the dream, a realistic assessment of your capacity is vital. Taking three highly demanding science HLs plus Math AA HL might lead to burnout or lower grades if you're not genuinely capable of managing the workload. Better to excel in the required subjects than to spread yourself too thin and underperform. Consult with your IB Coordinator and subject teachers early in your Diploma Programme to make informed choices.
Frequently asked questions
Choosing the right IB subjects for Natural Sciences requires strategic thinking. The non-negotiable core is Mathematics: Analysis and Approaches HL, plus two science HLs (Physics, Chemistry, or Biology). Physics and Chemistry HL offer the most versatility, while Chemistry and Biology HL are strong for life sciences. Avoid Math AI HL and taking only one science at HL. Prioritize achieving high predicted grades in these essential subjects, and only consider a fourth HL if it doesn't compromise your core performance. Your subject choices are a direct signal to universities about your preparedness and potential for a rigorous science degree.