Vitamins: Fat-Soluble vs Water-Soluble Classification (NEET)
Chemistry · Biomolecules · NEET
Vitamins are split into two groups by what dissolves them. Fat-soluble vitamins are A, D, E and K. They dissolve in fat and oil, get stored in your liver and fat tissue, and can become harmful if you take too much. Water-soluble vitamins are the B-group and vitamin C. They dissolve in water, are not stored, and leave the body in urine, so you need them daily. Memory hook: remember "ADEK" (say it like "a deck" of cards) for the four fat-soluble vitamins; everything else (B and C) is water-soluble.
Vitamins split into two groups. Fat-soluble A, D, E, K dissolve in fat, are stored in the body, and can be toxic in excess. Water-soluble B group and C dissolve in water, are not stored, and must be taken daily.
Your doubts, answered
Which vitamins are fat-soluble and which are water-soluble?
Only four vitamins are fat-soluble: A, D, E and K. Use the word ADEK to remember them. All the rest are water-soluble: the whole vitamin B group (B1, B2, B6, B12 and others) and vitamin C. So if a NEET question names any B vitamin or vitamin C, the answer is water-soluble. Any of A, D, E, K is fat-soluble.
Is vitamin C fat-soluble or water-soluble?
Vitamin C (ascorbic acid) is water-soluble. It dissolves in water, is not stored in the body, and extra amounts leave through urine. That is why you must eat vitamin C every day. Its deficiency causes scurvy. Students often guess wrong here, so remember: C is NOT in ADEK, so it is water-soluble.
Why are vitamins A, D, E and K fat-soluble?
These vitamins have large non-polar (oily) structures. By the rule 'like dissolves like', non-polar molecules dissolve in non-polar solvents like fat and oil, not in water. Because they mix with fat, your body stores them in the liver and in fatty tissue. This storage is why taking too much of A, D, E or K can build up and become toxic.
Which vitamins are stored in the body and which are not?
Fat-soluble vitamins (A, D, E, K) are stored in the liver and fat tissue, so you do not need them every single day. Water-soluble vitamins (B group and C) are NOT stored; the body removes the extra in urine. So water-soluble vitamins must be supplied regularly in the diet. This is a very common NEET distinguishing point.
Is vitamin B12 water-soluble?
Yes. Vitamin B12 (cyanocobalamin) is water-soluble, like all B-group vitamins. It is not stored in large amounts for long, and its deficiency causes pernicious anaemia (fewer healthy red blood cells). Remember: every B vitamin and vitamin C are water-soluble.
Why must water-soluble vitamins be taken daily but not fat-soluble ones?
Water-soluble vitamins (B and C) dissolve in water and are washed out of the body in urine. The body cannot keep a big store of them, so you must eat them daily. Fat-soluble vitamins (A, D, E, K) get stored in fat and liver, so a store lasts longer and daily intake is not strictly needed.
⚠️ The NEET trap ✗ Choosing that vitamin C or a B vitamin is fat-soluble, or that fat-soluble vitamins are excreted in urine. ✓ Only A, D, E, K are fat-soluble and stored in fat/liver. B-group and C are water-soluble and removed in urine, so they must be taken daily. 🧠 Fat-soluble = ADEK = stored (can be toxic in excess). Water-soluble = B and C = flushed out daily. If it is not in 'a deck' (ADEK), it goes down the drain.
Real NEET questions
NEET 2023 Phase 2
Cheilosis occurs due to deficiency of _________.
A · Pyridoxamine
B · Riboflavin ✓
C · Thiamine
D · Nicotinamide
Solution: Cheilosis (cracking at the corners of the mouth and lips) is caused by deficiency of vitamin B2, riboflavin. Riboflavin is a water-soluble vitamin, so it must be taken in the diet regularly. Pyridoxamine is a form of B6, thiamine is B1 (deficiency causes beri-beri), and nicotinamide is the amide of niacin/B3 (deficiency causes pellagra). All are water-soluble B vitamins. Correct answer: B.
NEET 2021
Deficiency of red blood cells (pernicious anaemia) is the deficiency disease of
A · Vitamin B1
B · Vitamin B2
C · Vitamin B12 ✓
D · Vitamin B6
Solution: Vitamin B12 (cyanocobalamin) is needed for the maturation of red blood cells. Its deficiency causes pernicious anaemia, where RBCs are low in number and low in haemoglobin. B12 is a water-soluble vitamin. B1 deficiency gives beri-beri, B2 gives cheilosis, and B6 gives convulsions. Correct answer: C.
ReNEET 2026
Match the vitamins in List-I with their sources in List-II. List-I: A. Vitamin A, B. Vitamin B12, C. Vitamin E, D. Vitamin K. List-II: I. meat, II. sunflower oil, III. green leafy vegetables, IV. carrots.
A · A-II, B-III, C-IV, D-I
B · A-IV, B-I, C-II, D-III ✓
C · A-IV, B-II, C-I, D-III
D · A-III, B-I, C-IV, D-II
Solution: Vitamin A comes from carrots (beta-carotene) so A-IV. Vitamin B12 comes from meat (an animal source) so B-I. Vitamin E comes from vegetable/sunflower oil so C-II. Vitamin K comes from green leafy vegetables so D-III. Note A, E and K are the fat-soluble ones here (sources are oily/plant foods) while B12 is water-soluble. Correct answer: B (A-IV, B-I, C-II, D-III).
Solved Biomolecules NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
What is the easiest trick to remember fat-soluble vitamins?
Remember the word ADEK, said like 'a deck' of cards. A, D, E and K are the four fat-soluble vitamins. Everything else, meaning the whole B group and vitamin C, is water-soluble.
Can fat-soluble vitamins be toxic?
Yes. Because A, D, E and K are stored in the liver and fat tissue, taking too much can build up in the body and cause toxicity. Water-soluble vitamins are less likely to build up because the extra is removed in urine.
Which vitamin deficiency causes scurvy?
Scurvy is caused by deficiency of vitamin C (ascorbic acid), a water-soluble vitamin. Since vitamin C is not stored, it must be eaten daily to prevent scurvy.
Are all B vitamins water-soluble?
Yes, every vitamin in the B group, including B1, B2, B6 and B12, is water-soluble. Along with vitamin C, they dissolve in water and are not stored in large amounts, so they are needed regularly.
Why does the body store fat-soluble vitamins but not water-soluble ones?
Fat-soluble vitamins dissolve in fat, so they get stored in fatty tissue and the liver. Water-soluble vitamins dissolve in water and are washed out in urine, so the body cannot hold a large store of them.
