Grapefruit vs orange: carbs, fiber and net carbs

For vitamin C, the orange wins. In USDA samples, raw navel oranges averaged 59 mg per 3.5 oz (100 g) against 38 mg in grapefruit. Half a grapefruit and one whole orange both weigh about 5.4 oz (154 g), and that orange carries about 86.5 mg, 96% of the Daily Value.

The bigger difference is about medicines. The FDA explains that grapefruit juice blocks CYP3A4, a gut enzyme that breaks some drugs down, so more reaches the blood. Yet across 51 studies, it cut blood levels of the blood pressure drugs aliskiren and celiprolol by about 80 to 90%. Orange is no automatic safe swap. The same review found orange and apple juice had comparable effects on certain drugs, and orange juice significantly cut absorption of the antifungal itraconazole in another review. These findings are about juice. The one case report that tested a whole grapefruit found no effect on the two drugs it tried, too little to rely on.

One myth to drop. Daily vitamin C did not prevent colds in community trials of 10,708 people.

If you take regular medicine, ask your pharmacist about both juices. If not, pick the one you enjoy and favor the whole fruit. In US cohorts, whole grapefruit went with slightly lower type 2 diabetes risk and fruit juice with slightly higher, an observational link.

Evidence behind this note

1. Level E Raw navel oranges averaged 59 mg vitamin C and 2.0 g fiber per 3.5 oz (100 g) in USDA samples, against 38 mg and 0.65 g for raw grapefruit. USDA FoodData Central, Foundation Foods, release 2026-04-30
2. Level E In US survey portions, half a grapefruit and one whole orange both count as 154 g, while a whole grapefruit is 308 g. USDA FNDDS 2021-2023, food codes 61101010 and 61119010
3. Level E One orange covers nearly the whole day's vitamin C and about an eighth of the day's fiber. USDA FNDDS 2021-2023, Orange, raw (fdc_id 2709171)
4. Level E The US FDA explains that grapefruit juice can block the gut enzyme CYP3A4, so more of some drugs enters the blood and stays longer. US Food and Drug Administration, Grapefruit Juice and Some Drugs Don't Mix, updated 2021
5. Level A A meta-analysis of 51 studies found grapefruit juice cut blood levels of the blood pressure drugs aliskiren and celiprolol by about 80 to 90%, and orange and apple juice had comparable effects on some drugs. Complement Ther Med, 2025
6. Level A In a meta-analysis of 51 studies, grapefruit juice cut blood exposure (AUC and Cmax) of the blood pressure drugs aliskiren and celiprolol by about 80-90%. Complement Ther Med, 2025
7. Level A A review of 73 studies on oral antifungals found orange juice significantly reduced how much itraconazole the body absorbs. Clin Pharmacokinet, 2025
8. Level D In the same case study, eating one whole grapefruit before the drug had no effect on nifedipine or amlodipine. Clin Exp Hypertens, 2010
9. Level E The FDA advises asking a doctor or pharmacist whether grapefruit juice interacts with your medication. US Food and Drug Administration, Grapefruit Juice and Some Drugs Don't Mix, updated 2021
10. Level A Taking vitamin C every day does not stop people catching colds, and it shortens a cold by about a twelfth at over 200 mg a day as a supplement, which is more than twice what an orange holds. Cochrane Database of Systematic Reviews, 2013
11. Level C Across three US cohorts, each 3 servings a week of whole grapefruit was linked to a 5% lower risk of type 2 diabetes (HR 0.95), while fruit juice was linked to 8% higher risk. BMJ, 2013

Written from the studies and agency guidance we hold for both foods, reviewed by the Bioma editorial system. How we verify.

Read more about these foods

• Grapefruit vs orange: the difference that matters is in the juice and your pills
• Grapefruit and your medicines: what the juice does
• Oranges: the fruit, the juice, and the 200 mg threshold

What the studies say

• Does grapefruit help with weight loss? Not beyond what a glass of water does
• Is grapefruit good during pregnancy? Untested, and the juice clashes with nifedipine

Rankings and guides

• Carbohydrates: what it does and how much you need
• Fiber: what it does and how much you need
• Which foods are highest in dietary fiber?
• Which foods are highest in carbohydrate?
• Added sugar: what it does and what the evidence shows
• Grapefruit: full nutrition facts
• Orange: full nutrition facts

• Grapefruit: USDA FoodData Central, Grapefruit, raw, white, all areas, FDC ID 174676 · full profile · all forms of grapefruit
• Orange: USDA FoodData Central, Oranges, raw, navels, FDC ID 746771 · full profile · all forms of orange

Each food is one USDA entry, chosen as it is usually eaten. Other cuts, brands and preparations differ; the links show them. % DV uses FDA Daily Values for adults. How we verify.